Haemophilus meningitis

Infectious Disease MONDO:0000889 Pathograph 22 Show in embeddings browser Bacterial meningitis

Haemophilus meningitis is bacterial meningitis caused by invasive Haemophilus influenzae, classically type b strains, after the organism colonizes the upper airway, invades blood, and reaches the meninges to replicate in cerebrospinal fluid and trigger acute meningeal inflammation.

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Classifications

Harrison's Part
INFECTIOUS DISEASES
⚙

Pathophysiology

7
Nasopharyngeal Haemophilus Acquisition
Respiratory exposure seeds the nasopharynx with an invasive H. influenzae lineage.
Downstream
Invasive Haemophilus Bacteremia Colonizing bacteria that escape mucosal containment enter the bloodstream.
Show evidence (1 reference)
PMID:30049648 SUPPORT BACKGROUND Human clinical
"The Gram-negative bacterium Haemophilus influenzae (H. influenzae) can commensally colonize the upper respiratory tract, but also cause life threatening disease including epiglottitis, sepsis and meningitis."
Supports upper-respiratory colonization as the early host phase for H. influenzae strains that go on to cause invasive disease.
Invasive Haemophilus Bacteremia
Bloodstream H. influenzae survives host clearance and disseminates to the central nervous system.
Downstream
PRP Capsule Immune Evasion Encapsulated Hib uses its PRP capsule to resist phagocytic and opsonic-complement clearance.
Meningeal Haemophilus Seeding Bacteria that survive the bloodstream interact with the blood-CSF and blood-brain barriers before entering the cerebrospinal-fluid compartment.
Fever Sustained invasive bacteremia produces systemic fever.
Show evidence (1 reference)
PMID:10470555 SUPPORT REVIEW SYNTHESIS Other
"using intranasal, intravenous, subcutaneous, or intraperitoneal inoculation, it is the bacterial and host factors that determine the development of bacteremia and the potential for a pathogen to invade the central nervous system that primarily are studied."
A review of experimental meningitis models frames bacteremia and subsequent central-nervous-system invasion as the pathogenic sequence this node represents.
PRP Capsule Immune Evasion
The Hib polyribosyl ribitol phosphate capsule is the major virulence factor and protects H. influenzae from phagocytosis and opsonization, favoring bloodstream survival.
complement activation GO:0006956 ↓ DECREASED Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased complement activation (GO:0006956). GO:0006956 is a biological process from the Gene Ontology.
Downstream
Meningeal Haemophilus Seeding Capsule-supported bacteremia lets invasive H. influenzae persist long enough to reach neurovascular barriers.
Show evidence (2 references)
PMID:34076491 SUPPORT REVIEW SYNTHESIS Other
"Its major virulence factor is the polyribosyl ribitol phosphate (PRP) polysaccharide capsule."
Identifies the PRP capsule as the defining Hib virulence structure.
PMID:30049648 SUPPORT BACKGROUND In vitro / ex vivo
"The H. influenzae capsule protects the bacteria against both phagocytosis and opsonization."
Supports the bloodstream immune-evasion function assigned to the capsule.
Meningeal Haemophilus Seeding
Hib and related encapsulated H. influenzae strains cross the blood-cerebrospinal-fluid barrier through choroid plexus epithelial cells and enter the cerebrospinal-fluid compartment.
choroid plexus epithelial cell CL:0000706 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves choroid plexus epithelial cell (CL:0000706). CL:0000706 is a cell type from the Cell Ontology.
choroid plexus UBERON:0001886 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in choroid plexus (UBERON:0001886). UBERON:0001886 is an anatomical location from the Uberon multi-species anatomy ontology. cerebrospinal fluid UBERON:0001359 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in cerebrospinal fluid (UBERON:0001359). UBERON:0001359 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Hib LOS-Induced Cytokine Release Once bacteria seed cerebrospinal fluid, bacterial lipooligosaccharide elicits the local cytokine cascade that drives purulent meningitis.
Show evidence (2 references)
PMID:30049648 SUPPORT BACKGROUND In vitro / ex vivo
"To enter the central nervous system (CNS) the bacteria generally have to cross either the blood-brain barrier (BBB) or the blood-cerebrospinal fluid barrier (BSCFB)."
Establishes the blood-CSF barrier and blood-brain barrier as candidate CNS-entry routes for H. influenzae.
PMID:30049648 SUPPORT In vitro / ex vivo
"We find that Hib can adhere to and invade into HIBCPP cells."
Directly supports Hib adhesion to and invasion of the human choroid plexus papilloma blood-CSF-barrier cell model.
Hib LOS-Induced Cytokine Release
Hib lipooligosaccharide shed in cerebrospinal fluid induces early TNF-alpha and interleukin-1 beta production, the initiating cytokine signal of meningeal inflammation.
tumor necrosis factor production GO:0032640 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves tumor necrosis factor production (GO:0032640). GO:0032640 is a biological process from the Gene Ontology. interleukin-1 beta production GO:0032611 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves interleukin-1 beta production (GO:0032611). GO:0032611 is a biological process from the Gene Ontology.
subarachnoid space UBERON:0000315 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in subarachnoid space (UBERON:0000315). UBERON:0000315 is an anatomical location from the Uberon multi-species anatomy ontology. cerebrospinal fluid UBERON:0001359 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in cerebrospinal fluid (UBERON:0001359). UBERON:0001359 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Meningeal Neutrophilic Inflammation Early CSF cytokine release precedes and drives the neutrophilic inflammatory influx.
Show evidence (2 references)
PMID:2794062 SUPPORT Model organism
"TNF activity was first detected 45 min after intracisternal (IC) injection of 20 ng Hib LOS and white blood cells (WBC) first appeared 75 min later."
The rabbit Hib-LOS model places CSF TNF production 45 min after LOS, ahead of the leukocyte influx at 75 min.
PMID:2373990 SUPPORT Model organism
"These data provide evidence for a seminal role of TNF-alpha and IL-1 beta in the initial events of meningeal inflammation."
Homologous rabbit-cytokine experiments identify TNF-alpha and IL-1 beta as the initiating mediators of meningeal inflammation.
Meningeal Neutrophilic Inflammation
LOS-driven cytokines recruit neutrophils into the subarachnoid space, producing the neutrophilic meningeal inflammation that generates the acute clinical meningitis syndrome.
neutrophil CL:0000775 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves neutrophil (CL:0000775). CL:0000775 is a cell type from the Cell Ontology.
leukocyte migration GO:0050900 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves leukocyte migration (GO:0050900). GO:0050900 is a biological process from the Gene Ontology.
subarachnoid space UBERON:0000315 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in subarachnoid space (UBERON:0000315). UBERON:0000315 is an anatomical location from the Uberon multi-species anatomy ontology. cerebrospinal fluid UBERON:0001359 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in cerebrospinal fluid (UBERON:0001359). UBERON:0001359 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Blood-Brain Barrier Breakdown Leukocyte influx and cytokines amplify permeability injury at the blood-brain barrier.
Vomiting Acute meningeal inflammation produces vomiting.
Poor feeding Acute meningeal illness produces poor feeding in infants.
Lethargy Meningeal inflammation produces lethargy.
Seizure Cortical irritation from meningeal inflammation produces seizures.
Subdural effusion Meningeal inflammation can produce a subdural effusion.
Show evidence (1 reference)
PMID:2794062 SUPPORT Model organism
"TNF activity was first detected 45 min after intracisternal (IC) injection of 20 ng Hib LOS and white blood cells (WBC) first appeared 75 min later."
The same rabbit model places the white-blood-cell influx 75 min after LOS, the neutrophilic inflammation this node represents.
Blood-Brain Barrier Breakdown
H. influenzae type b hematogenous meningitis increases blood-brain-barrier permeability, allowing serum proteins and inflammatory mediators to enter cerebrospinal fluid and drive edema-producing CNS injury.
cerebrospinal fluid UBERON:0001359 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in cerebrospinal fluid (UBERON:0001359). UBERON:0001359 is an anatomical location from the Uberon multi-species anatomy ontology.
Animal models
Infant rat hematogenous Hib meningitis Rat recapitulates The infant-rat hematogenous model measures albumin leakage into cerebrospinal fluid during H. influenzae type b meningitis.
Downstream
Sensorineural hearing impairment Inflammatory injury to the cochlear nerve produces sensorineural hearing loss.
Hydrocephalus Barrier breakdown and impaired CSF dynamics produce hydrocephalus.
Motor deficit Cortical and subcortical injury produces focal motor deficits.
Developmental delay Neonatal and infant brain injury produces neurodevelopmental delay as a long-term sequela.
Show evidence (1 reference)
PMID:9184127 SUPPORT Model organism
"In the model of hematogenous meningitis, the mean CSF penetration was significantly greater in animals with H. influenzae type b meningitis than in those with meningitis due to K1 E. coli or type III group B streptococcus."
Supports blood-brain-barrier permeability as a downstream tissue injury in hematogenous Hib meningitis.
⬡

Pathograph

Use Group by to collapse related nodes into one box. Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Haemophilus meningitis Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

10
Digestive 2
Vomiting OCCASIONAL HP:0002013 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Vomiting (HP:0002013). HP:0002013 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"The presenting symptoms in decreasing order of frequency were fever 86%, vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%."
Vomiting was present in 29% of this pediatric bacterial meningitis cohort.
Poor feeding OCCASIONAL Feeding difficulties in infancy HP:0008872 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Feeding difficulties in infancy (HP:0008872). HP:0008872 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"The presenting symptoms in decreasing order of frequency were fever 86%, vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%."
Poor feeding was present in 19% of this pediatric bacterial meningitis cohort.
Ear 1
Sensorineural hearing impairment OCCASIONAL HP:0000407 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sensorineural hearing impairment (HP:0000407). HP:0000407 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"Complications occurred in 26% of the patients and included subdural effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay 9%, hydrocephalus 6% and motor deficit 30%."
Hearing loss occurred in 14% of patients in a pediatric bacterial meningitis series dominated by H. influenzae cases.
Metabolism 1
Fever VERY_FREQUENT HP:0001945 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Fever (HP:0001945). HP:0001945 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"The presenting symptoms in decreasing order of frequency were fever 86%, vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%."
Fever was the most common presenting symptom in a pediatric bacterial meningitis cohort in which H. influenzae caused 66% of cases.
Musculoskeletal 1
Motor deficit FREQUENT Functional motor deficit HP:0004302 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Functional motor deficit (HP:0004302). HP:0004302 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"Complications occurred in 26% of the patients and included subdural effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay 9%, hydrocephalus 6% and motor deficit 30%."
Motor deficit occurred in 30% of this pediatric bacterial meningitis cohort.
Nervous System 5
Seizure OCCASIONAL HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"The presenting symptoms in decreasing order of frequency were fever 86%, vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%."
Seizure was present at presentation in 14% of children in this Haemophilus-predominant bacterial meningitis cohort.
Hydrocephalus OCCASIONAL HP:0000238 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hydrocephalus (HP:0000238). HP:0000238 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"Complications occurred in 26% of the patients and included subdural effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay 9%, hydrocephalus 6% and motor deficit 30%."
Hydrocephalus occurred in 6% of patients in a pediatric bacterial meningitis series dominated by H. influenzae cases.
Lethargy OCCASIONAL HP:0001254 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Lethargy (HP:0001254). HP:0001254 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"The presenting symptoms in decreasing order of frequency were fever 86%, vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%."
Lethargy was present in 14% of this pediatric bacterial meningitis cohort.
Subdural effusion OCCASIONAL Subdural hygroma HP:6001070 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Subdural effusion, annotated with Subdural hygroma (HP:6001070). HP:6001070 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"Complications occurred in 26% of the patients and included subdural effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay 9%, hydrocephalus 6% and motor deficit 30%."
Subdural effusion occurred in 23% of this pediatric bacterial meningitis cohort.
Developmental delay OCCASIONAL Global developmental delay HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:9570646 SUPPORT Human clinical
"Complications occurred in 26% of the patients and included subdural effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay 9%, hydrocephalus 6% and motor deficit 30%."
Developmental delay occurred in 9% of this pediatric bacterial meningitis cohort.
💊

Medical Actions

4
Adjunctive dexamethasone
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: dexamethasone CHEBI:41879 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses dexamethasone (CHEBI:41879). CHEBI:41879 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Anti-inflammatory corticosteroid given before or with antibiotics to reduce cytokine-driven neurologic injury, with the clearest hearing-loss reduction signal in Haemophilus influenzae meningitis.
Mechanism Target:
INHIBITS Hib LOS-Induced Cytokine Release — Dexamethasone suppresses Hib-LOS-induced TNF production and meningeal inflammation, dampening the inflammatory burst that follows antibiotic killing.
Show evidence (1 reference)
PMID:2794062 SUPPORT Model organism
"Dexamethasone (DXM) (1 mg/kg per i.v.) given 1 h before or simultaneously with IC Hib LOS reduced significantly TNF activity and meningeal inflammation."
The rabbit Hib-LOS model demonstrates dexamethasone suppression of the TNF-linked meningeal inflammatory response.
Show evidence (2 references)
PMID:20824838 SUPPORT REVIEW SYNTHESIS Human clinical
"Corticosteroids were associated with lower rates of severe hearing loss (RR 0.67, 95% CI 0.51 to 0.88), any hearing loss (RR 0.76, 95% CI 0.64 to 0.89) and neurological sequelae (RR 0.83, 95% CI 0.69 to 1.00)."
The Cochrane meta-analysis supports adjunctive corticosteroids as a way to reduce post-meningitic hearing loss and neurologic sequelae.
PMID:20824838 SUPPORT REVIEW SYNTHESIS Human clinical
"Subgroup analyses for causative organisms showed that corticosteroids reduced severe hearing loss in Haemophilus influenzae meningitis (RR 0.34, 95% CI 0.20 to 0.59)"
The organism-specific subgroup showed a severe-hearing-loss reduction for H. influenzae meningitis.
Third-generation cephalosporin therapy
Action: Antibiotic TherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Antibiotic Therapy (NCIT:C15620). NCIT:C15620 is a clinical intervention from the NCI Thesaurus. NCIT:C15620
Agent: ceftriaxone CHEBI:29007 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses ceftriaxone (CHEBI:29007). CHEBI:29007 is a therapeutic agent from Chemical Entities of Biological Interest. cefotaxime CHEBI:204928 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses cefotaxime (CHEBI:204928). CHEBI:204928 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Empiric third-generation cephalosporins (ceftriaxone or cefotaxime) are first-line antimicrobial therapy; ampicillin-chloramphenicol is an alternative where cephalosporins are unavailable, and cephalosporins are required for strains that produce beta-lactamase.
Mechanism Target:
INHIBITS Meningeal Haemophilus Seeding — Bactericidal cephalosporins clear H. influenzae from blood and CSF, halting meningeal seeding.
INHIBITS Invasive Haemophilus Bacteremia — Systemic cephalosporin therapy clears the invasive bloodstream infection.
Show evidence (1 reference)
PMID:19375903 SUPPORT REVIEW SYNTHESIS Other
"When third generation cephalosporins are not available, ampicillin-chloramphenicol combination may be used as an alternative empiric treatment, however both resistance pattern as well as availability should be considered while prescribing empiric therapy of community acquired ABM."
A Cochrane overview establishes third-generation cephalosporins as the primary empiric therapy, with ampicillin-chloramphenicol as the alternative.
Hib PRP-protein conjugate vaccination
Action: VaccinationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Vaccination (NCIT:C15346). NCIT:C15346 is a clinical intervention from the NCI Thesaurus. NCIT:C15346
Platform: Vaccine
PRP-protein conjugate vaccines induce protective anti-PRP antibody and have sharply reduced invasive Hib disease including meningitis; anti-PRP antibody opsonizes the capsule, acting at the immune-evasion step.
Mechanism Target:
INHIBITS PRP Capsule Immune Evasion — Vaccine-induced anti-PRP antibody opsonizes the capsule, neutralizing the immune-evasion function that enables invasive disease.
Show evidence (1 reference)
PMID:33247582 SUPPORT PRIMARY RESULT Human clinical
"Conjugate vaccines effectively reduced the incidence of Haemophilus influenzae type b, Neisseria meningitidis serogroup C, and 10 pneumococcal serotypes"
National surveillance shows conjugate vaccination sharply reduced invasive Hib disease incidence.
Rifampin chemoprophylaxis for close contacts
Action: Antibiotic ProphylaxisNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Antibiotic Prophylaxis (NCIT:C51993). NCIT:C51993 is a clinical intervention from the NCI Thesaurus. NCIT:C51993
Agent: rifampicin CHEBI:28077 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses rifampicin (CHEBI:28077). CHEBI:28077 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Rifampin prophylaxis of close and household contacts eliminates nasopharyngeal carriage and controls secondary Hib cases and outbreaks.
Mechanism Target:
INHIBITS Nasopharyngeal Haemophilus Acquisition — Rifampin prophylaxis clears nasopharyngeal carriage in contacts, blocking acquisition and secondary transmission.
Show evidence (1 reference)
PMID:3485275 SUPPORT PRIMARY RESULT Human clinical
"The outbreak ended following rifampin prophylaxis of all community members younger than 15 years of age"
An outbreak study shows rifampin prophylaxis of contacts controlled secondary Hib disease.
📈

Progression

4
Nasopharyngeal colonization
H. influenzae colonizes the upper respiratory tract, usually asymptomatically.
Invasive bacteremia
The organism breaches the mucosa and establishes high-grade bacteremia.
Meningitis
Bloodborne organisms seed the meninges, producing acute bacterial meningitis with fever, vomiting, lethargy and seizures.
Neurological sequelae
Survivors may develop hearing loss, hydrocephalus, motor deficits and developmental delay.
🦠

Infectious Agent

1
Haemophilus influenzae
Gram-negative nasopharyngeal bacterium whose invasive encapsulated type b lineage historically caused pediatric bacterial meningitis.
Haemophilus influenzae NCBITaxon:727 NCBI Taxonomy (NCBITaxon)
Show evidence (1 reference)
PMID:30049648 SUPPORT BACKGROUND Human clinical
"The Gram-negative bacterium Haemophilus influenzae (H. influenzae) can commensally colonize the upper respiratory tract, but also cause life threatening disease including epiglottitis, sepsis and meningitis."
Background in a blood-CSF-barrier invasion study identifies H. influenzae as an upper-respiratory colonizer that can cause meningitis.
↔️

Transmission

1
Respiratory Haemophilus acquisition
H. influenzae reaches a new host through respiratory secretions, colonizes the nasopharynx, and can invade blood before meningeal infection develops.
Show evidence (1 reference)
PMID:30049648 SUPPORT BACKGROUND Human clinical
"The Gram-negative bacterium Haemophilus influenzae (H. influenzae) can commensally colonize the upper respiratory tract, but also cause life threatening disease including epiglottitis, sepsis and meningitis."
Places H. influenzae in the upper respiratory tract before invasive meningitis.
🐁

Animal Models

1
Infant rat hematogenous Hib meningitis
Infant rats develop hematogenous H. influenzae type b meningitis with measurable blood-brain-barrier permeability after peripheral inoculation.
Species
Rat
Publication
PMID:9184127
Pathograph links
Blood-Brain Barrier Breakdown recapitulates fidelity: moderate observes: organism The infant-rat hematogenous model measures albumin leakage into cerebrospinal fluid during H. influenzae type b meningitis.
Limitations: The model uses infant rats and experimentally delivered bacteria, so it does not recapitulate natural human nasopharyngeal acquisition.
Show evidence (2 references)
PMID:9184127 SUPPORT Model organism
"In the model of hematogenous meningitis, the mean CSF penetration was significantly greater in animals with H. influenzae type b meningitis than in those with meningitis due to K1 E. coli or type III group B streptococcus."
Directly supports the infant rat as a hematogenous Hib meningitis model with quantifiable blood-brain-barrier permeability.
+ 1 more reference
{ }

Source YAML

click to show 
name: Haemophilus meningitis
creation_date: "2026-09-30T02:18:19Z"
description: >-
  Haemophilus meningitis is bacterial meningitis caused by invasive
  Haemophilus influenzae, classically type b strains, after the organism
  colonizes the upper airway, invades blood, and reaches the meninges to
  replicate in cerebrospinal fluid and trigger acute meningeal inflammation.
category: Infectious Disease
disease_term:
  preferred_term: haemophilus meningitis
  term:
    id: MONDO:0000889
    label: haemophilus meningitis
parents:
- Bacterial meningitis
synonyms:
- Haemophilus influenzae meningitis
- Hib meningitis
infectious_agent:
- name: Haemophilus influenzae
  infectious_agent_term:
    preferred_term: Haemophilus influenzae
    term:
      id: NCBITaxon:727
      label: Haemophilus influenzae
  description: >-
    Gram-negative nasopharyngeal bacterium whose invasive encapsulated type b
    lineage historically caused pediatric bacterial meningitis.
  evidence:
  - reference: PMID:30049648
    reference_title: Capsule and fimbriae modulate the invasion of Haemophilus influenzae in a human blood-cerebrospinal fluid barrier model.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      The Gram-negative bacterium Haemophilus influenzae (H. influenzae) can
      commensally colonize the upper respiratory tract, but also cause life
      threatening disease including epiglottitis, sepsis and meningitis.
    explanation: >-
      Background in a blood-CSF-barrier invasion study identifies H.
      influenzae as an upper-respiratory colonizer that can cause meningitis.
agent_life_cycle:
  description: >-
    H. influenzae is a human upper-respiratory organism; invasive encapsulated
    lineages colonize human hosts without an arthropod or animal vector and can
    spill from the nasopharynx into blood and cerebrospinal-fluid disease.
  hosts:
  - preferred_term: Homo sapiens
    role: nasopharyngeal host and clinical host
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  evidence:
  - reference: PMID:30049648
    reference_title: Capsule and fimbriae modulate the invasion of Haemophilus influenzae in a human blood-cerebrospinal fluid barrier model.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      The Gram-negative bacterium Haemophilus influenzae (H. influenzae) can
      commensally colonize the upper respiratory tract, but also cause life
      threatening disease including epiglottitis, sepsis and meningitis.
    explanation: >-
      Supports the human upper-airway phase that precedes invasive H.
      influenzae disease.
classifications:
  harrisons_chapter:
  - classification_value: INFECTIOUS_DISEASES
transmission:
- name: Respiratory Haemophilus acquisition
  description: >-
    H. influenzae reaches a new host through respiratory secretions, colonizes
    the nasopharynx, and can invade blood before meningeal infection develops.
  evidence:
  - reference: PMID:30049648
    reference_title: Capsule and fimbriae modulate the invasion of Haemophilus influenzae in a human blood-cerebrospinal fluid barrier model.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      The Gram-negative bacterium Haemophilus influenzae (H. influenzae) can
      commensally colonize the upper respiratory tract, but also cause life
      threatening disease including epiglottitis, sepsis and meningitis.
    explanation: >-
      Places H. influenzae in the upper respiratory tract before invasive
      meningitis.
pathophysiology:
- name: Nasopharyngeal Haemophilus Acquisition
  role: trigger
  description: >-
    Respiratory exposure seeds the nasopharynx with an invasive H. influenzae
    lineage.
  biological_scale: ORGANISM
  downstream:
  - target: Invasive Haemophilus Bacteremia
    causal_link_type: DIRECT
    description: >-
      Colonizing bacteria that escape mucosal containment enter the bloodstream.
  evidence:
  - reference: PMID:30049648
    reference_title: Capsule and fimbriae modulate the invasion of Haemophilus influenzae in a human blood-cerebrospinal fluid barrier model.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: >-
      The Gram-negative bacterium Haemophilus influenzae (H. influenzae) can
      commensally colonize the upper respiratory tract, but also cause life
      threatening disease including epiglottitis, sepsis and meningitis.
    explanation: >-
      Supports upper-respiratory colonization as the early host phase for H.
      influenzae strains that go on to cause invasive disease.
- name: Invasive Haemophilus Bacteremia
  description: >-
    Bloodstream H. influenzae survives host clearance and disseminates to the
    central nervous system.
  biological_scale: ORGANISM
  downstream:
  - target: PRP Capsule Immune Evasion
    causal_link_type: DIRECT
    description: >-
      Encapsulated Hib uses its PRP capsule to resist phagocytic and
      opsonic-complement clearance.
  - target: Meningeal Haemophilus Seeding
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Bacteria that survive the bloodstream interact with the blood-CSF and
      blood-brain barriers before entering the cerebrospinal-fluid compartment.
  - target: Fever
    causal_link_type: DIRECT
    description: >-
      Sustained invasive bacteremia produces systemic fever.
  evidence:
  - reference: PMID:10470555
    reference_title: Models of experimental bacterial meningitis. Role and limitations.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      using intranasal, intravenous, subcutaneous, or intraperitoneal
      inoculation, it is the bacterial and host factors that determine the
      development of bacteremia and the potential for a pathogen to invade the
      central nervous system that primarily are studied.
    explanation: >-
      A review of experimental meningitis models frames bacteremia and
      subsequent central-nervous-system invasion as the pathogenic sequence this
      node represents.
- name: PRP Capsule Immune Evasion
  conforms_to: "polysaccharide_conjugate_t_dependent_switching#Polysaccharide Capsule-Mediated Mucosal Colonization and Complement Evasion"
  description: >-
    The Hib polyribosyl ribitol phosphate capsule is the major virulence factor
    and protects H. influenzae from phagocytosis and opsonization, favoring
    bloodstream survival.
  biological_scale: CELLULAR
  biological_processes:
  - preferred_term: complement activation
    modifier: DECREASED
    term:
      id: GO:0006956
      label: complement activation
  downstream:
  - target: Meningeal Haemophilus Seeding
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Capsule-supported bacteremia lets invasive H. influenzae persist long
      enough to reach neurovascular barriers.
  evidence:
  - reference: PMID:34076491
    reference_title: Invasive Haemophilus influenzae Infections after 3 Decades of Hib Protein Conjugate Vaccine Use.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Its major virulence factor is the polyribosyl ribitol phosphate (PRP)
      polysaccharide capsule.
    explanation: >-
      Identifies the PRP capsule as the defining Hib virulence structure.
  - reference: PMID:30049648
    reference_title: Capsule and fimbriae modulate the invasion of Haemophilus influenzae in a human blood-cerebrospinal fluid barrier model.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: BACKGROUND
    snippet: >-
      The H. influenzae capsule protects the bacteria against both phagocytosis
      and opsonization.
    explanation: >-
      Supports the bloodstream immune-evasion function assigned to the capsule.
- name: Meningeal Haemophilus Seeding
  description: >-
    Hib and related encapsulated H. influenzae strains cross the
    blood-cerebrospinal-fluid barrier through choroid plexus epithelial cells
    and enter the cerebrospinal-fluid compartment.
  biological_scale: ORGANISM
  cell_types:
  - preferred_term: choroid plexus epithelial cell
    term:
      id: CL:0000706
      label: choroid plexus epithelial cell
  locations:
  - preferred_term: choroid plexus
    term:
      id: UBERON:0001886
      label: choroid plexus
  - preferred_term: cerebrospinal fluid
    term:
      id: UBERON:0001359
      label: cerebrospinal fluid
  downstream:
  - target: Hib LOS-Induced Cytokine Release
    causal_link_type: DIRECT
    description: >-
      Once bacteria seed cerebrospinal fluid, bacterial lipooligosaccharide
      elicits the local cytokine cascade that drives purulent meningitis.
  evidence:
  - reference: PMID:30049648
    reference_title: Capsule and fimbriae modulate the invasion of Haemophilus influenzae in a human blood-cerebrospinal fluid barrier model.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: BACKGROUND
    snippet: >-
      To enter the central nervous system (CNS) the bacteria generally have to
      cross either the blood-brain barrier (BBB) or the blood-cerebrospinal
      fluid barrier (BSCFB).
    explanation: >-
      Establishes the blood-CSF barrier and blood-brain barrier as candidate
      CNS-entry routes for H. influenzae.
  - reference: PMID:30049648
    reference_title: Capsule and fimbriae modulate the invasion of Haemophilus influenzae in a human blood-cerebrospinal fluid barrier model.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      We find that Hib can adhere to and invade into HIBCPP cells.
    explanation: >-
      Directly supports Hib adhesion to and invasion of the human choroid
      plexus papilloma blood-CSF-barrier cell model.
- name: Hib LOS-Induced Cytokine Release
  description: >-
    Hib lipooligosaccharide shed in cerebrospinal fluid induces early TNF-alpha
    and interleukin-1 beta production, the initiating cytokine signal of
    meningeal inflammation.
  biological_scale: TISSUE
  biological_processes:
  - preferred_term: tumor necrosis factor production
    term:
      id: GO:0032640
      label: tumor necrosis factor production
  - preferred_term: interleukin-1 beta production
    term:
      id: GO:0032611
      label: interleukin-1 beta production
  locations:
  - preferred_term: subarachnoid space
    term:
      id: UBERON:0000315
      label: subarachnoid space
  - preferred_term: cerebrospinal fluid
    term:
      id: UBERON:0001359
      label: cerebrospinal fluid
  downstream:
  - target: Meningeal Neutrophilic Inflammation
    causal_link_type: DIRECT
    description: >-
      Early CSF cytokine release precedes and drives the neutrophilic
      inflammatory influx.
  evidence:
  - reference: PMID:2794062
    reference_title: Tumor necrosis factor in mediating experimental Haemophilus influenzae type B meningitis.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      TNF activity was first detected 45 min after intracisternal (IC) injection
      of 20 ng Hib LOS and white blood cells (WBC) first appeared 75 min later.
    explanation: >-
      The rabbit Hib-LOS model places CSF TNF production 45 min after LOS, ahead
      of the leukocyte influx at 75 min.
  - reference: PMID:2373990
    reference_title: Tumor necrosis factor alpha/cachectin and interleukin 1 beta initiate meningeal inflammation.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      These data provide evidence for a seminal role of TNF-alpha and IL-1 beta
      in the initial events of meningeal inflammation.
    explanation: >-
      Homologous rabbit-cytokine experiments identify TNF-alpha and IL-1 beta as
      the initiating mediators of meningeal inflammation.
- name: Meningeal Neutrophilic Inflammation
  description: >-
    LOS-driven cytokines recruit neutrophils into the subarachnoid space,
    producing the neutrophilic meningeal inflammation that generates the acute
    clinical meningitis syndrome.
  biological_scale: TISSUE
  cell_types:
  - preferred_term: neutrophil
    term:
      id: CL:0000775
      label: neutrophil
  biological_processes:
  - preferred_term: leukocyte migration
    term:
      id: GO:0050900
      label: leukocyte migration
  locations:
  - preferred_term: subarachnoid space
    term:
      id: UBERON:0000315
      label: subarachnoid space
  - preferred_term: cerebrospinal fluid
    term:
      id: UBERON:0001359
      label: cerebrospinal fluid
  downstream:
  - target: Blood-Brain Barrier Breakdown
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >-
      Leukocyte influx and cytokines amplify permeability injury at the
      blood-brain barrier.
  - target: Vomiting
    description: >-
      Acute meningeal inflammation produces vomiting.
  - target: Poor feeding
    description: >-
      Acute meningeal illness produces poor feeding in infants.
  - target: Lethargy
    description: >-
      Meningeal inflammation produces lethargy.
  - target: Seizure
    description: >-
      Cortical irritation from meningeal inflammation produces seizures.
  - target: Subdural effusion
    description: >-
      Meningeal inflammation can produce a subdural effusion.
  evidence:
  - reference: PMID:2794062
    reference_title: Tumor necrosis factor in mediating experimental Haemophilus influenzae type B meningitis.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      TNF activity was first detected 45 min after intracisternal (IC) injection
      of 20 ng Hib LOS and white blood cells (WBC) first appeared 75 min later.
    explanation: >-
      The same rabbit model places the white-blood-cell influx 75 min after LOS,
      the neutrophilic inflammation this node represents.
- name: Blood-Brain Barrier Breakdown
  description: >-
    H. influenzae type b hematogenous meningitis increases blood-brain-barrier
    permeability, allowing serum proteins and inflammatory mediators to enter
    cerebrospinal fluid and drive edema-producing CNS injury.
  biological_scale: TISSUE
  locations:
  - preferred_term: cerebrospinal fluid
    term:
      id: UBERON:0001359
      label: cerebrospinal fluid
  downstream:
  - target: Sensorineural hearing impairment
    description: >-
      Inflammatory injury to the cochlear nerve produces sensorineural hearing
      loss.
  - target: Hydrocephalus
    description: >-
      Barrier breakdown and impaired CSF dynamics produce hydrocephalus.
  - target: Motor deficit
    description: >-
      Cortical and subcortical injury produces focal motor deficits.
  - target: Developmental delay
    description: >-
      Neonatal and infant brain injury produces neurodevelopmental delay as a
      long-term sequela.
  evidence:
  - reference: PMID:9184127
    reference_title: Blood-brain barrier permeability during the development of experimental bacterial meningitis in the rat.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      In the model of hematogenous meningitis, the mean CSF penetration was
      significantly greater in animals with H. influenzae type b meningitis than
      in those with meningitis due to K1 E. coli or type III group B
      streptococcus.
    explanation: >-
      Supports blood-brain-barrier permeability as a downstream tissue injury in
      hematogenous Hib meningitis.
phenotypes:
- name: Fever
  description: Fever is a common presenting sign in pediatric bacterial meningitis cohorts dominated by H. influenzae.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The presenting symptoms in decreasing order of frequency were fever 86%,
      vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%.
    explanation: >-
      Fever was the most common presenting symptom in a pediatric bacterial
      meningitis cohort in which H. influenzae caused 66% of cases.
- name: Seizure
  description: Seizures can occur during acute Haemophilus-predominant pediatric bacterial meningitis and can persist as a post-meningitic seizure disorder.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The presenting symptoms in decreasing order of frequency were fever 86%,
      vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%.
    explanation: >-
      Seizure was present at presentation in 14% of children in this
      Haemophilus-predominant bacterial meningitis cohort.
- name: Sensorineural hearing impairment
  description: Hearing loss is a clinically important neurologic sequela of Hib-predominant childhood bacterial meningitis.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Complications occurred in 26% of the patients and included subdural
      effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay
      9%, hydrocephalus 6% and motor deficit 30%.
    explanation: >-
      Hearing loss occurred in 14% of patients in a pediatric bacterial
      meningitis series dominated by H. influenzae cases.
- name: Hydrocephalus
  description: Hydrocephalus is an occasional sequela of Haemophilus-predominant pediatric bacterial meningitis.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Hydrocephalus
    term:
      id: HP:0000238
      label: Hydrocephalus
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Complications occurred in 26% of the patients and included subdural
      effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay
      9%, hydrocephalus 6% and motor deficit 30%.
    explanation: >-
      Hydrocephalus occurred in 6% of patients in a pediatric bacterial
      meningitis series dominated by H. influenzae cases.
- name: Vomiting
  frequency: OCCASIONAL
  description: Vomiting is a common presenting symptom of childhood H. influenzae meningitis.
  phenotype_term:
    preferred_term: Vomiting
    term:
      id: HP:0002013
      label: Vomiting
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The presenting symptoms in decreasing order of frequency were fever 86%,
      vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%.
    explanation: Vomiting was present in 29% of this pediatric bacterial meningitis cohort.
- name: Poor feeding
  frequency: OCCASIONAL
  description: Poor feeding is a common presenting sign in infants with H. influenzae meningitis.
  phenotype_term:
    preferred_term: Feeding difficulties in infancy
    term:
      id: HP:0008872
      label: Feeding difficulties in infancy
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The presenting symptoms in decreasing order of frequency were fever 86%,
      vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%.
    explanation: Poor feeding was present in 19% of this pediatric bacterial meningitis cohort.
- name: Lethargy
  frequency: OCCASIONAL
  description: Lethargy is a common presenting sign of childhood H. influenzae meningitis.
  phenotype_term:
    preferred_term: Lethargy
    term:
      id: HP:0001254
      label: Lethargy
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The presenting symptoms in decreasing order of frequency were fever 86%,
      vomiting 29%, poor feeding 19%, seizure 14% and lethargy 14%.
    explanation: Lethargy was present in 14% of this pediatric bacterial meningitis cohort.
- name: Subdural effusion
  frequency: OCCASIONAL
  description: >-
    Subdural effusion is the most common intracranial complication of childhood
    H. influenzae meningitis.
  phenotype_term:
    preferred_term: Subdural effusion
    term:
      id: HP:6001070
      label: Subdural hygroma
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Complications occurred in 26% of the patients and included subdural
      effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay
      9%, hydrocephalus 6% and motor deficit 30%.
    explanation: Subdural effusion occurred in 23% of this pediatric bacterial meningitis cohort.
- name: Motor deficit
  frequency: FREQUENT
  description: Focal motor deficits are a frequent complication of childhood H. influenzae meningitis.
  phenotype_term:
    preferred_term: Functional motor deficit
    term:
      id: HP:0004302
      label: Functional motor deficit
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Complications occurred in 26% of the patients and included subdural
      effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay
      9%, hydrocephalus 6% and motor deficit 30%.
    explanation: Motor deficit occurred in 30% of this pediatric bacterial meningitis cohort.
- name: Developmental delay
  frequency: OCCASIONAL
  description: Neurodevelopmental delay is a long-term sequela of childhood H. influenzae meningitis.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:9570646
    reference_title: Childhood bacterial meningitis in Saudi Arabia.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Complications occurred in 26% of the patients and included subdural
      effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay
      9%, hydrocephalus 6% and motor deficit 30%.
    explanation: Developmental delay occurred in 9% of this pediatric bacterial meningitis cohort.
treatments:
- name: Adjunctive dexamethasone
  description: >-
    Anti-inflammatory corticosteroid given before or with antibiotics to reduce
    cytokine-driven neurologic injury, with the clearest hearing-loss reduction
    signal in Haemophilus influenzae meningitis.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: dexamethasone
      term:
        id: CHEBI:41879
        label: dexamethasone
  target_mechanisms:
  - target: Hib LOS-Induced Cytokine Release
    treatment_effect: INHIBITS
    description: >-
      Dexamethasone suppresses Hib-LOS-induced TNF production and meningeal
      inflammation, dampening the inflammatory burst that follows antibiotic
      killing.
    evidence:
    - reference: PMID:2794062
      reference_title: Tumor necrosis factor in mediating experimental Haemophilus influenzae type B meningitis.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Dexamethasone (DXM) (1 mg/kg per i.v.) given 1 h before or
        simultaneously with IC Hib LOS reduced significantly TNF activity and
        meningeal inflammation.
      explanation: >-
        The rabbit Hib-LOS model demonstrates dexamethasone suppression of the
        TNF-linked meningeal inflammatory response.
  evidence:
  - reference: PMID:20824838
    reference_title: Corticosteroids for acute bacterial meningitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Corticosteroids were associated with lower rates of severe hearing loss
      (RR 0.67, 95% CI 0.51 to 0.88), any hearing loss (RR 0.76, 95% CI 0.64 to
      0.89) and neurological sequelae (RR 0.83, 95% CI 0.69 to 1.00).
    explanation: >-
      The Cochrane meta-analysis supports adjunctive corticosteroids as a way to
      reduce post-meningitic hearing loss and neurologic sequelae.
  - reference: PMID:20824838
    reference_title: Corticosteroids for acute bacterial meningitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      Subgroup analyses for causative organisms showed that corticosteroids
      reduced severe hearing loss in Haemophilus influenzae meningitis (RR 0.34,
      95% CI 0.20 to 0.59)
    explanation: >-
      The organism-specific subgroup showed a severe-hearing-loss reduction for
      H. influenzae meningitis.
- name: Third-generation cephalosporin therapy
  description: >-
    Empiric third-generation cephalosporins (ceftriaxone or cefotaxime) are
    first-line antimicrobial therapy; ampicillin-chloramphenicol is an
    alternative where cephalosporins are unavailable, and cephalosporins are
    required for strains that produce beta-lactamase.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Antibiotic Therapy
    term:
      id: NCIT:C15620
      label: Antibiotic Therapy
    therapeutic_agent:
    - preferred_term: ceftriaxone
      term:
        id: CHEBI:29007
        label: ceftriaxone
    - preferred_term: cefotaxime
      term:
        id: CHEBI:204928
        label: cefotaxime
  target_mechanisms:
  - target: Meningeal Haemophilus Seeding
    treatment_effect: INHIBITS
    description: >-
      Bactericidal cephalosporins clear H. influenzae from blood and CSF,
      halting meningeal seeding.
  - target: Invasive Haemophilus Bacteremia
    treatment_effect: INHIBITS
    description: >-
      Systemic cephalosporin therapy clears the invasive bloodstream infection.
  evidence:
  - reference: PMID:19375903
    reference_title: "Treatment of bacterial meningitis: an overview of Cochrane systematic reviews."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: >-
      When third generation cephalosporins are not available,
      ampicillin-chloramphenicol combination may be used as an alternative
      empiric treatment, however both resistance pattern as well as
      availability should be considered while prescribing empiric therapy of
      community acquired ABM.
    explanation: >-
      A Cochrane overview establishes third-generation cephalosporins as the
      primary empiric therapy, with ampicillin-chloramphenicol as the
      alternative.
- name: Hib PRP-protein conjugate vaccination
  description: >-
    PRP-protein conjugate vaccines induce protective anti-PRP antibody and have
    sharply reduced invasive Hib disease including meningitis; anti-PRP antibody
    opsonizes the capsule, acting at the immune-evasion step.
  therapeutic_modality: VACCINE
  treatment_term:
    preferred_term: Vaccination
    term:
      id: NCIT:C15346
      label: Vaccination
  target_mechanisms:
  - target: PRP Capsule Immune Evasion
    treatment_effect: INHIBITS
    description: >-
      Vaccine-induced anti-PRP antibody opsonizes the capsule, neutralizing the
      immune-evasion function that enables invasive disease.
  evidence:
  - reference: PMID:33247582
    reference_title: "Changing Epidemiology of Bacterial Meningitis Since Introduction of Conjugate Vaccines: 3 Decades of National Meningitis Surveillance in The Netherlands."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      Conjugate vaccines effectively reduced the incidence of Haemophilus
      influenzae type b, Neisseria meningitidis serogroup C, and 10 pneumococcal
      serotypes
    explanation: >-
      National surveillance shows conjugate vaccination sharply reduced invasive
      Hib disease incidence.
- name: Rifampin chemoprophylaxis for close contacts
  description: >-
    Rifampin prophylaxis of close and household contacts eliminates
    nasopharyngeal carriage and controls secondary Hib cases and outbreaks.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Antibiotic Prophylaxis
    term:
      id: NCIT:C51993
      label: Antibiotic Prophylaxis
    therapeutic_agent:
    - preferred_term: rifampicin
      term:
        id: CHEBI:28077
        label: rifampicin
  target_mechanisms:
  - target: Nasopharyngeal Haemophilus Acquisition
    treatment_effect: INHIBITS
    description: >-
      Rifampin prophylaxis clears nasopharyngeal carriage in contacts, blocking
      acquisition and secondary transmission.
  evidence:
  - reference: PMID:3485275
    reference_title: "Haemophilus influenzae type b disease in an Amish population: studies of the effects of genetic factors, immunization, and rifampin prophylaxis on the course of an outbreak."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    snippet: >-
      The outbreak ended following rifampin prophylaxis of all community members
      younger than 15 years of age
    explanation: >-
      An outbreak study shows rifampin prophylaxis of contacts controlled
      secondary Hib disease.
progression:
- phase: Nasopharyngeal colonization
  notes: H. influenzae colonizes the upper respiratory tract, usually asymptomatically.
- phase: Invasive bacteremia
  notes: The organism breaches the mucosa and establishes high-grade bacteremia.
- phase: Meningitis
  notes: >-
    Bloodborne organisms seed the meninges, producing acute bacterial meningitis
    with fever, vomiting, lethargy and seizures.
- phase: Neurological sequelae
  notes: >-
    Survivors may develop hearing loss, hydrocephalus, motor deficits and
    developmental delay.
animal_models:
- name: Infant rat hematogenous Hib meningitis
  species: Rat
  publication: PMID:9184127
  description: >-
    Infant rats develop hematogenous H. influenzae type b meningitis with
    measurable blood-brain-barrier permeability after peripheral inoculation.
  modeled_mechanisms:
  - target: Blood-Brain Barrier Breakdown
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: >-
      The infant-rat hematogenous model measures albumin leakage into
      cerebrospinal fluid during H. influenzae type b meningitis.
    limitations: >-
      The model uses infant rats and experimentally delivered bacteria, so it
      does not recapitulate natural human nasopharyngeal acquisition.
    evidence:
    - reference: PMID:9184127
      reference_title: Blood-brain barrier permeability during the development of experimental bacterial meningitis in the rat.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        In the model of hematogenous meningitis, the mean CSF penetration was
        significantly greater in animals with H. influenzae type b meningitis
        than in those with meningitis due to K1 E. coli or type III group B
        streptococcus.
      explanation: >-
        Directly supports the infant rat as a hematogenous Hib meningitis model
        with quantifiable blood-brain-barrier permeability.
    - reference: PMID:10470555
      reference_title: Models of experimental bacterial meningitis. Role and limitations.
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        because adult animals will not reliably develop meningitis after
        intranasal or intraperitoneal challenge, infant animals are used.
      explanation: >-
        Review synthesis explains the age limitation that motivates infant
        animals in hematogenous experimental meningitis models.
📚

References & Deep Research

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Evaluations and curation notes (1)

Round-1 review fixes: antibiotics, vaccine, prophylaxis, phenotypes, wiring, node split, regrades · 2026-10-20T18:57:40Z · View source

Addressed the seven blocking review items. (1) Added a third-generation cephalosporin treatment (ceftriaxone CHEBI:29007, cefotaxime CHEBI:204928; PMID:19375903) targeting bacteremia and meningeal seeding. (2) Added Hib PRP-protein conjugate vaccination (VACCINE modality, NCIT:C15346; PMID:33247582) targeting PRP Capsule Immune Evasion, and rifampin chemoprophylaxis (rifampicin CHEBI:28077; PMID:3485275) targeting nasopharyngeal acquisition. (3) Added six phenotypes from the already-cached PMID:9570646 - vomiting 29%, poor feeding 19%, lethargy 14%, subdural effusion 23% (term omitted, no HP match), motor deficit 30% (HP:0004302), developmental delay 9% (HP:0001263) - and corrected the fever band FREQUENT to VERY_FREQUENT (86%). (4) Regraded the four colonization-sentence evidence items from IN_VITRO to HUMAN_CLINICAL+BACKGROUND (the quote describes human carriage and clinical disease); genuine in-vitro choroid-plexus results left IN_VITRO. (5) Replaced the bacteremia node's misplaced PRP-capsule snippet with a bacteremia->CNS dissemination snippet (PMID:10470555); the PRP snippet stays correctly on the PRP Capsule node, which already carried it. (6) Wired the pathograph to its phenotypes (bacteremia->fever, meningeal inflammation->vomiting/poor feeding/lethargy/seizure/subdural effusion, BBB breakdown->hearing loss/hydrocephalus/motor deficit/developmental delay) so list-disconnected-phenotypes is now 10/10; split the bundled LOS-TNF node into a cytokine-release node and a neutrophilic-inflammation node (the rabbit model separates TNF at 45 min from WBC influx at 75 min) and removed the unsupported macrophage cell type, retargeting the Meningeal Seeding downstream edge and the dexamethasone treatment onto the cytokine node. (7) Added a progression block (colonization, bacteremia, meningitis, sequelae), clearing NO_PROGRESSION. Also moved the deep-research session log out of notes into this record: the Falcon request fell back to OpenScientist, all 49 references resolved, four generated epidemiology/vaccine quotes were non-exact and not curated, and preflight-dr skipped gene-identity checks (no RO:0004003 gene on MONDO:0000889). validate, validate-terms, validate-disorders (LRV, 31/31) and the connectivity/grading gates all pass. Deferred the optional diagnosis and prevalence sections, which need Hib-specific sources not yet cached.

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Haemophilus Meningitis (MONDO:0000889): A Comprehensive Disease Characterization
openscientist-autonomous 49 citations 2026-09-29T19:36:58.196575

Haemophilus Meningitis (MONDO:0000889): A Comprehensive Disease Characterization

Infectious Disease Knowledge Base Report — compiled from iterative literature synthesis (59 citations, 12 recorded findings)

Summary

Haemophilus meningitis (MONDO:0000889; ICD-10 G00.0 "Haemophilus meningitis"; MeSH D008586 "Meningitis, Haemophilus") is an acute bacterial (pyogenic) meningitis caused by the human-restricted Gram-negative coccobacillus Haemophilus influenzae, historically and predominantly serotype b (Hib). It is an infectious, non-genetic disease: there is no causal human gene, no Mendelian inheritance, and no OMIM entry for the disease itself. The information base is aggregated disease-level epidemiology, clinical cohorts, randomized trials, and experimental animal/cell-barrier models rather than individual-patient genetic data.

The pathophysiology is a well-defined causal chain: the polyribosylribitol phosphate (PRP) capsule allows Hib to resist phagocytosis and complement, survive in the bloodstream, and invade the blood–CSF barrier in a polarized fashion; once in the subarachnoid space, shed lipooligosaccharide (LOS) triggers a TNF-α / IL-1β-driven meningeal inflammatory cascade that produces cerebral edema, raised intracranial pressure, cochlear injury, and neuronal damage. Clinically the disease presents with fever, headache, neck stiffness, photophobia and altered mental status; case fatality reaches up to ~30% and roughly 50% of survivors develop neurological sequelae (deafness, seizures, cognitive impairment, hydrocephalus). Treatment is a third-generation cephalosporin (ceftriaxone or cefotaxime) plus adjunctive dexamethasone, which reduces hearing loss with the strongest evidence in Hib meningitis when given before or with the first antibiotic dose.

The single most important fact about this disease in the modern era is the transformative impact of PRP–protein conjugate vaccination. Hib was the leading cause of childhood bacterial meningitis in the pre-vaccine era; conjugate vaccines drove incidence down by 96–98% in surveillance settings. Residual and re-emerging disease is now driven by non-b serotypes — notably H. influenzae type a (Hia) in Indigenous North American children — as well as nontypeable strains and disease in older/comorbid adults. Meningitis overall remains a major global killer (GBD 2023: ~259,000 deaths, 2.54 million cases, >⅓ of deaths in children under 5), concentrated in low-income settings and the African meningitis belt.

Section 1 — Disease Information

Overview. Haemophilus meningitis is inflammation of the leptomeninges and subarachnoid CSF caused by Haemophilus influenzae, a fastidious Gram-negative coccobacillus that is an obligate human commensal/pathogen of the upper respiratory tract. Encapsulated strains (serotypes a–f, distinguished by capsular polysaccharide) cause invasive disease; serotype b (Hib) historically accounted for the overwhelming majority of meningitis cases. Prior to conjugate vaccination, "Hib was the leading cause of meningitis in children prior to the introduction of an effective vaccination" (PMID: 21999651).

Key identifiers.

Resource Identifier
MONDO MONDO:0000889 (Haemophilus meningitis)
ICD-10 G00.0 (Haemophilus meningitis)
ICD-11 1D01.0 (Bacterial meningitis) / infectious meningitis codes
MeSH D008586 "Meningitis, Haemophilus"
MeSH (organism) D006193 "Haemophilus influenzae"
NCBI Taxonomy Haemophilus influenzae — txid727
OMIM Not applicable (infectious disease, no Mendelian gene)
Orphanet Not a rare disease in the Orphanet sense (common infection)

Synonyms / alternative names. Haemophilus influenzae meningitis; Hib meningitis; H. influenzae type b meningitis; pyogenic/bacterial meningitis due to H. influenzae; historically "influenzal meningitis" (a misnomer from the erroneous 1890s belief that H. influenzae caused influenza).

Data source type. Aggregated, disease-level resources (national surveillance, clinical cohorts, RCTs, meta-analyses, experimental models). Not individual-patient EHR-derived and not genetic-variant-derived.

Section 2 — Etiology

Causal factor: infectious. The disease is caused by Haemophilus influenzae; it is not genetic and not environmental in origin, although host and environmental factors modulate susceptibility.

Risk factors (environmental / host): - Age: highest risk in infants and young children, especially 6–23 months; "Haemophilus influenzae type b (Hib) causes invasive infections almost exclusively in under-fives with those aged 6-23 months being the most vulnerable" (PMID: 38070126). Young age (<1 year) is an independent predictor of poor outcome (PMID: 34732790). - Lack of vaccination / incomplete Hib immunization. - Immunocompromise: asplenia, HIV, complement deficiency — high-risk groups for invasive encapsulated-bacterial disease (PMID: 36287171). - CSF shunts / neurosurgical devices (nosocomial/device-associated meningitis) (PMID: 40249832). - Indigenous ethnicity (American Indian/Alaska Native) — markedly elevated invasive H. influenzae risk: "Invasive Haemophilus influenzae type b (Hib) disease is a serious bacterial infection that disproportionally affects American Indian and Alaska Native (AI/AN) populations" (PMID: 39264849). - Crowding / close-contact settings (households, communities) facilitate transmission of nasopharyngeal carriage. - Male sex was an independent risk factor for poor outcome in shunt-associated pediatric meningitis (OR 2.82) (PMID: 40249832).

Genetic risk factors. No single causal or susceptibility gene is established. In an Amish Hib outbreak investigation, inbreeding was not a significant risk factor and cases shared no common HLA haplotype (PMID: 3485275) — arguing against a strong monogenic host susceptibility. Known immunodeficiencies (complement C2–C9, properdin, antibody deficiencies, asplenia) predispose broadly to encapsulated-organism invasive disease.

Protective factors. - Anti-PRP antibody (naturally acquired or vaccine-induced) is protective; the long-term protective threshold is ~1 µg/mL anti-PRP (PMID: 38070126). - Hib conjugate vaccination (primary protective intervention — see Sections 12–13). - Breastfeeding and herd immunity (reduced carriage) are recognized protective influences in the broader literature.

Gene–environment interactions. Not established for this infectious disease; the dominant "interaction" is between host immune status (age-dependent antibody repertoire, immunodeficiency) and pathogen exposure/carriage.

Section 3 — Phenotypes

Haemophilus meningitis produces the phenotypes of acute bacterial meningitis. The classic triad (fever, neck stiffness, altered mental status) is frequently incomplete: only ~26% show the full triad but ~83% have ≥2 of 4 cardinal features (PMID: 28879886).

Phenotype Type HPO suggestion Onset/severity Frequency
Fever Clinical sign HP:0001945 Acute, moderate–severe Very frequent
Headache Symptom HP:0002315 Acute Very frequent
Nuchal rigidity / meningismus Clinical sign HP:0031179 Acute Frequent (can be subtle/absent early)
Photophobia Symptom HP:0000613 Acute Frequent
Altered mental status / reduced consciousness Clinical sign HP:0001259 / HP:0001298 Acute Frequent; GCS<13 predicts poor outcome
Seizures Clinical sign HP:0001250 Acute; may become chronic disorder ~10% (seizure disorder as sequela)
Sensorineural hearing loss Lab/clinical HP:0000407 Acute onset, often permanent ~14%
Subdural effusion Physical/imaging HP:0012595 Acute ~23%
Hydrocephalus Physical/imaging HP:0000238 Subacute ~6%
Developmental delay / cognitive impairment Cognitive HP:0001263 / HP:0100543 Long-term sequela ~9%
Focal motor deficit Clinical sign HP:0007360 Acute/long-term Present in cohorts
CSF neutrophilic pleocytosis Lab abnormality HP:0012229 Acute Near-universal

Per-complication frequencies are drawn from a predominantly-Hib pediatric cohort where "Complications occurred in 26% of the patients and included subdural effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay 9%, hydrocephalus 6%" (PMID: 9570646). Meningeal signs can be subtle early: a confirmed adult H. influenzae meningitis case presented with rapid hearing loss and initially absent neck stiffness (PMID: 40509725).

Quality-of-life impact. Permanent sensorineural deafness, epilepsy, motor deficits, and cognitive/developmental impairment substantially reduce QoL in survivors; ~50% of survivors develop neurological complications (PMID: 33807653).

Section 4 — Genetic / Molecular Information

Not applicable to host genetics. Haemophilus meningitis has no causal human gene, no pathogenic germline/somatic variant, no modifier gene, no host epigenetic driver, and no chromosomal abnormality. It is not a heritable disorder; there is no ClinVar/OMIM/HGMD entry for the disease.

The relevant "molecular genetics" are those of the pathogen: - cap b locus (bexA–D and type-specific region) encodes biosynthesis/export of the PRP capsule — the principal virulence determinant. "Its major virulence factor is the polyribosyl ribitol phosphate (PRP) polysaccharide capsule" (PMID: 34076491). - Lipooligosaccharide (LOS) biosynthesis genes — LOS (endotoxin) is the key inflammatory trigger. - Fimbriae/pili and outer-membrane proteins modulate adhesion and blood–CSF-barrier invasion (PMID: 30049648; PMID: 41318968). - vapD/vapX toxin–antitoxin locus enhances intracellular survival in epithelial and brain microvascular endothelial cells (PMID: 15274747).

Serotype is defined by capsular polysaccharide structure; molecular modeling shows serotype a and b capsular polysaccharides differ conformationally enough to lack cross-protective antibody recognition (PMID: 34491462) — relevant to serotype-replacement disease.

Section 5 — Environmental Information

Infectious agent (organism): Haemophilus influenzae (NCBI:txid727), serotype b predominant historically; serotypes a, e, f and nontypeable strains increasingly relevant. Transmission is person-to-person via respiratory droplets and nasopharyngeal carriage. Asymptomatic nasopharyngeal carriage among healthcare workers and community members serves as a reservoir; carriage prevalence for H. influenzae was 11.8% among paediatric healthcare workers in Benin (none serotype b) (PMID: 40847276).

Environmental / lifestyle factors that increase transmission or susceptibility: crowding, daycare attendance, household exposure, tobacco smoke exposure, and lack of vaccination. There are no chemical toxins or occupational exposures that cause this disease. CHEBI-relevant molecular entities in pathogenesis: lipopolysaccharide/lipooligosaccharide (CHEBI:16412) and PRP (ribitol phosphate polymer).

Section 6 — Mechanism / Pathophysiology

Ordered causal chain

  1. Nasopharyngeal colonization by encapsulated H. influenzae (usually Hib) leads to local mucosal adherence (fimbriae, OMPs) and, in susceptible hosts, mucosal invasion.
  2. Mucosal invasion results in bacteremia; the PRP capsule confers resistance to phagocytosis and complement-mediated killing, enabling bloodstream survival and high-grade bacteremia. (Demonstrated: capsule is the major virulence factor — [PMID: 34076491].)
  3. Sustained bacteremia leads to interaction with the blood–CSF barrier (choroid plexus epithelium) and blood–brain barrier (microvascular endothelium). Hib invades the barrier in a polarized manner from the basolateral "blood" side and/or by transcytosis. (Demonstrated in HIBCPP cell model — [PMID: 30049648]; transcytosis inferred as a shared CNS-entry route — [PMID: 20026234].)
  4. Barrier penetration results in bacterial entry into the subarachnoid space / CSF, an immunologically permissive compartment with low complement and antibody.
  5. Bacterial multiplication and autolysis/LOS shedding trigger release of lipooligosaccharide (endotoxin) into CSF.
  6. LOS induces resident macrophages/microglia and meningeal cells to produce TNF-α and IL-1β — the seminal early cytokines. In the rabbit model TNF activity appears in CSF within 45 min of intracisternal LOS, preceding leukocyte influx by ~75 min. (Demonstrated — [PMID: 2373990]; [PMID: 2794062].)
  7. TNF-α/IL-1β cause upregulation of endothelial adhesion molecules and chemokines, leading to neutrophilic pleocytosis (leukocyte influx into CSF). Combined TNF-α + IL-1β act synergistically. (Demonstrated — [PMID: 2373990].)
  8. Neutrophil influx and inflammation result in blood–brain-barrier breakdown (increased permeability), vasogenic and cytotoxic cerebral edema, altered CSF dynamics, and raised intracranial pressure. In infant rats Hib causes greater BBB albumin penetration than other pathogens, correlating with CSF TNF ([PMID: 9184127]).
  9. Edema + inflammation + vasculitis/thrombosis branch into:
  10. (a) Global injury: raised ICP → reduced cerebral perfusion → ischemia/hypoxia → neuronal necrosis/apoptosis → coma, death.
  11. (b) Cochlear injury: inflammation tracks along the cochlear aqueduct to the inner ear → cochlear/eighth-nerve inflammation → sensorineural hearing loss. (Dexamethasone reduces cochlear-nerve inflammation in infant rats — [PMID: 1759817].)
  12. (c) Local complications: subdural effusion, hydrocephalus (impaired CSF resorption), seizures, focal deficits.
  13. These processes manifest clinically as fever, meningismus, altered consciousness, seizures; and, in survivors, as long-term sequelae (deafness, epilepsy, cognitive impairment, hydrocephalus).

Detail by category

  • Molecular pathways: LOS/LPS → TLR4/CD14 signaling → NF-κB activation → transcription of TNF-α, IL-1β, IL-6, chemokines (inferred canonical pathway; the cytokine outputs are directly demonstrated). Anti-inflammatory IL-10 counter-regulates: intracisternal IL-10 >1 µg significantly reduced CSF TNF-α and lactate (PMID: 9359724).
  • Cellular processes: acute inflammation, leukocyte recruitment, endothelial activation, apoptosis/necrosis of neurons, disruption of tight-junction proteins (occludin, claudins, JAMs) by bacterial virulence factors (PMID: 41318968).
  • Immune involvement: innate immune over-activation drives injury; anti-PRP humoral immunity is protective. Specific cytokine inhibitors (sTNFR, IL-1RA) did not consistently modulate LOS-driven meningeal inflammation, suggesting redundancy/broad stimulus (PMID: 7798656).
  • Tissue damage mechanisms: oxidative stress, ischemia (vasculitis/thrombosis), cytotoxic + vasogenic edema, elevated CSF lactate.
  • Suggested GO / CL / UBERON terms: GO:0006954 inflammatory response; GO:0032640 tumor necrosis factor production; GO:0032611 IL-1β production; GO:0050900 leukocyte migration; GO:0006909 phagocytosis; CL:0000235 macrophage; CL:0000129 microglial cell; CL:0000775 neutrophil; CL:0002139 endothelial cell of vascular tree; CL:0000066 epithelial cell (choroid plexus); UBERON:0002361 meninges; UBERON:0001359 CSF; UBERON:0001886 choroid plexus.

Section 7 — Anatomical Structures Affected

  • Primary organ/system: central nervous system — meninges (UBERON:0002361) and subarachnoid space/CSF (UBERON:0001359); the brain (UBERON:0000955) is secondarily affected via edema, ischemia, and abscess/effusion.
  • Secondary organ involvement / complications: inner ear/cochlea (UBERON:0001844) → deafness; cerebral ventricles → hydrocephalus; subdural space → subdural effusion/empyema; systemic sepsis may cause transient myocardial dysfunction (neurogenic stunned myocardium) — reported with H. influenzae CNS infection in children (PMID: 40751825).
  • Body systems: nervous, immune, and (via bacteremia) cardiovascular/systemic.
  • Tissue/cell level: choroid plexus epithelium and brain microvascular endothelial cells (barrier invasion sites); meningeal macrophages/microglia (cytokine production); neutrophils (CSF influx); neurons (injury); cochlear hair cells / eighth cranial nerve (hearing loss).
  • Subcellular: endothelial/epithelial tight junctions (GO:0005923 bicellular tight junction); plasma membrane signaling complexes (TLR4). Bacterial LOS acts at the cell surface.
  • Localization / lateralization: the meningeal process is diffuse and bilateral; complications (subdural effusion, focal deficits, hearing loss) may be unilateral or asymmetric.

Section 8 — Temporal Development

  • Onset: typically acute (hours to a few days); most common in infants/young children (peak 6–23 months). Adult cases occur, often in older/comorbid hosts.
  • Progression: rapidly progressive if untreated; delays in diagnosis/treatment worsen outcome (PMID: 35419149). With effective antibiotics the acute illness is typically self-limited over 7–14 days of treatment; shorter (≤7 day) courses may be non-inferior for uncomplicated cases (PMID: 37870611).
  • Disease course: monophasic acute illness (not relapsing/remitting), but with potential permanent sequelae. Critical intervention window: early antibiotics + dexamethasone before/with the first antibiotic dose is the key window to prevent hearing loss (PMID: 22789668).
  • Remission: treatment-induced recovery in survivors; sequelae may be permanent.

Section 9 — Inheritance and Population

  • Inheritance: None — not a genetic disease (no AD/AR/X-linked/mitochondrial pattern; not applicable).
  • Epidemiology (pre-vaccine): Hib was the leading cause of childhood bacterial meningitis. In a Kuwait pediatric series H. influenzae accounted for 45.6% of bacterial meningitis episodes; 88% of cases were in children <5 years (PMID: 2607574).
  • Epidemiology (post-vaccine): conjugate vaccines produced 96–98% reductions. Netherlands surveillance (1989–2019, 17,393 episodes): overall bacterial-meningitis incidence fell from 6.37 to 1.58 per 100,000/yr (IRR 0.25); Hib IRRs 0.02–0.04 (PMID: 33247582).
  • Current global burden: GBD 2023 estimated 259,000 meningitis deaths and 2.54 million incident cases (all causes); children <5 accounted for >⅓ of deaths (86,600) (PMID: 41911930). An 80-year meta-analysis (371 studies, 157,656 episodes) found H. influenzae caused 22% of episodes with an identified pathogen and a case-fatality of 11% (95% CI 10–13%) — lower than pneumococcus (24%) or Listeria (27%) (PMID: 39093565).
  • Geographic distribution: highest burden in low-income countries and the African meningitis belt; residual/re-emergent Hia disease concentrated in Indigenous North American (Alaska Native, American Indian) children.
  • Population demographics: male predominance in some cohorts; strong age skew toward under-5s; ethnic disparity (AI/AN populations). Alaska Hia surveillance: average annual incidence 17.8/100,000 in children <5 vs 0.3 in ≥5 years (PMID: 40071574).

Section 10 — Diagnostics

  • Lumbar puncture / CSF analysis is definitive. Bacterial meningitis CSF shows neutrophilic pleocytosis, low glucose (hypoglycorrhachia), elevated protein, elevated lactate, and elevated opening pressure.
  • Gram stain: H. influenzae appears as Gram-negative coccobacilli.
  • Culture: CSF and blood culture confirm the organism and enable antimicrobial susceptibility testing (essential given β-lactamase-mediated ampicillin resistance). Culture remains indispensable (PMID: 42256222).
  • Antigen detection: latex agglutination for the PRP capsular antigen (adjunct, especially after antibiotic pretreatment).
  • Multiplex PCR (BioFire FilmArray Meningitis/Encephalitis panel): detects 14 pathogens including H. influenzae directly from CSF in ~1 hour: "The FilmArray Meningitis/Encephalitis (ME) Panel provides multiplex molecular detection of 14 pathogens within ∼1 h" (PMID: 42679643). In one evaluation, bacterial/fungal targets showed sensitivity 100%, specificity 94.9%, NPV 100% vs culture (PMID: 42388946). PCR markedly increases pathogen detection over culture in meningitis, particularly after antibiotic pretreatment (PMID: 40280145). Panels are adjuncts, not standalone replacements for culture (PMID: 42256222; PMID: 42684933).
  • Imaging: CT/MRI to detect complications (subdural effusion, hydrocephalus, infarction, edema) and before LP if raised-ICP/mass concern.
  • Differential diagnosis: pneumococcal and meningococcal meningitis (other pyogenic causes), viral/aseptic meningitis (lymphocytic pleocytosis, normal glucose — e.g., enteroviral [PMID: 41362530], drug-induced [PMID: 40827196]), tuberculous and cryptococcal meningitis ([PMID: 39998376]).
  • Genetic/omics testing: not applicable for host diagnosis. Pathogen molecular typing (serotyping, WGS) is used for surveillance.

Section 11 — Outcome / Prognosis

  • Mortality: case fatality up to ~30% for bacterial meningitis broadly (PMID: 33807653); H. influenzae-specific pooled case-fatality ~11% (PMID: 39093565), lower than pneumococcal disease.
  • Morbidity: ~50% of survivors develop neurological complications (PMID: 33807653); sequelae include deafness, seizures, cognitive impairment, hydrocephalus, motor deficits.
  • Prognostic factors: treatment setting/resources (Angola vs Finland OR 11.91), depressed consciousness (GCS<13, OR 4.58), seizures (OR 1.96), age <1 year (OR 1.55), and pneumococcal (vs Hib) etiology (PMID: 34732790). Dismal outcome (death/severe sequelae/deafness) occurred in 54% in Angola, 31% in Latin America, 5% in Finland — illustrating that outcome is dominated by setting and presenting severity.
  • Recovery: with prompt appropriate therapy most survivors recover; permanent deficits (especially deafness) are the principal residual disability.

Section 12 — Treatment

Empiric antibiotics: third-generation cephalosporins — ceftriaxone or cefotaxime — are first-line (NCIT: Ceftriaxone C574; Cefotaxime C349). They are equivalent to conventional ampicillin-chloramphenicol in outcome where organisms are sensitive, but β-lactamase-producing Hib requires cephalosporins (PMID: 19375903). Where cephalosporins are unavailable, ampicillin–chloramphenicol is an alternative.

Adjunctive dexamethasone (NCIT: C459): reduces hearing loss and neurological sequelae, with the strongest, organism-specific benefit in Hib meningitis. Cochrane meta-analysis (25 RCTs, 4,121 participants): severe hearing loss RR 0.67 (95% CI 0.51–0.88), any hearing loss RR 0.74 (0.63–0.87), neurological sequelae RR 0.83 (0.69–1.00); mortality reduction non-significant (PMID: 20824838). Subgroup: corticosteroids "reduced severe hearing loss in Haemophilus influenzae meningitis (RR 0.34, 95% CI 0.20 to 0.59)" (PMID: 20824838). Benefit is clearest in high-income settings and requires timing before or with the first antibiotic dose (PMID: 22789668). Mechanistically, dexamethasone suppresses LOS-induced CSF TNF (PMID: 2794062).

Treatment duration: shorter (≤7 days) courses may be non-inferior to longer courses for uncomplicated childhood meningitis (PMID: 37870611).

Supportive care: ICU-level management of raised ICP, seizures, fluid/electrolyte balance (SIADH), and hemodynamic support; audiology follow-up and rehabilitation for sequelae. Experimental immunomodulation (IL-10) reduces CSF TNF in models but is not clinical (PMID: 9359724); specific cytokine inhibitors were ineffective in models (PMID: 7798656).

Pharmacogenomics / gene therapy / cell therapy / targeted-immunotherapy: not applicable to this infectious disease.

Section 13 — Prevention

Primary prevention — vaccination (the cornerstone). PRP–protein conjugate vaccines (PRP-T, PRP-OMP, HbOC) generate protective anti-PRP antibody. "As a result of widespread use of the vaccines, the incidence of Hib infections, and their associated morbidity and mortality, has fallen dramatically across the globe" (PMID: 34590133). Protective anti-PRP threshold ~1 µg/mL; seroprotection rates ~74% in a Nigerian cohort (PMID: 38070126). NCIT: Haemophilus b Conjugate Vaccine (C1213).

Tailored recommendations: ACIP (2024) preferentially recommends PRP-OMP-containing Hib vaccine for American Indian/Alaska Native infants due to higher invasive-disease risk and earlier disease onset (PMID: 39264849). A serotype a (Hia) conjugate vaccine is in development, motivated by serotype-replacement disease and lack of a/b cross-protection (PMID: 34491462).

Chemoprophylaxis: rifampin for close/household contacts controls transmission and secondary cases — an Amish Hib outbreak ended after rifampin prophylaxis was extended to all community members <15 years (PMID: 3485275). NCIT: Rifampin (C777).

Secondary/tertiary prevention: early LP, rapid empiric antibiotics, adjunctive dexamethasone to prevent sequelae; audiological screening; cochlear implantation for post-meningitic deafness; targeted vaccination of high-risk groups (asplenia, HIV, complement deficiency) (PMID: 36287171). WHO's "Defeating meningitis by 2030" roadmap frames the global prevention strategy (PMID: 39006487).

Section 14 — Other Species / Natural Disease

Haemophilus influenzae is human-restricted; there is no significant natural reservoir or naturally occurring H. influenzae meningitis in companion animals or wildlife. Related Haemophilus/Glaesserella species cause veterinary disease (e.g., Glaesserella (Haemophilus) parasuis causes Glässer's disease/meningitis in swine; Avibacterium (Haemophilus) paragallinarum in poultry), but these are distinct organisms. Zoonotic potential: none for H. influenzae. NCBI Taxonomy: H. influenzae txid727; humans Homo sapiens txid9606. VBO/breed: not applicable.

Section 15 — Model Organisms

  • Infant rat (principal in vivo model): 5-day-old rats develop hematogenous Hib meningitis after intraperitoneal inoculation (10⁴–10⁵ CFU), with reproducible bacteremia, weight loss, lethargy, and mortality; "because adult animals will not reliably develop meningitis after intranasal or intraperitoneal challenge, infant animals are used" (PMID: 10470555). Anti-LPS inner-core mAb (MAHI 3) raised survival from 10–17% to 60–90% (PMID: 10623558). The model recapitulates BBB permeability changes (PMID: 9184127) and cochlear-nerve inflammation reducible by dexamethasone (PMID: 1759817).
  • Rabbit intracisternal LOS/Hib model: dissects the cytokine cascade (TNF-α/IL-1β kinetics, IL-10/dexamethasone modulation) (PMID: 2373990; PMID: 2794062; PMID: 9359724).
  • Cell-barrier models: human choroid plexus papilloma (HIBCPP) blood–CSF barrier model and human brain microvascular endothelial cells (HBMEC) model bacterial invasion, polarity, and tight-junction disruption (PMID: 30049648; PMID: 15274747; PMID: 41318968).

Recapitulation / limitations: models faithfully reproduce bacteremia→CNS invasion, cytokine-driven inflammation, BBB permeability, and cochlear injury, and were pivotal in validating adjunctive dexamethasone. Limitations: age-restriction (only infant animals), inoculum route differs from natural mucosal acquisition, and species differences in immune response.

Key Findings (with statistical evidence)

Finding 1 — Conjugate vaccines produced a dramatic global decline from Hib's pre-vaccine dominance

Hib was the single most common cause of childhood bacterial meningitis before vaccination. Netherlands national surveillance (1989–2019, 17,393 episodes) showed overall bacterial meningitis incidence fell from 6.37 to 1.58 per 100,000/yr (IRR 0.25, 95% CI 0.23–0.26; P<.001), with conjugate vaccines reducing Hib incidence at IRRs of 0.02–0.04 (P<.001): "Conjugate vaccines effectively reduced the incidence of Haemophilus influenzae type b… (IRRs, .02–.04; P < .001)" (PMID: 33247582); "the incidence of Hib infections… has fallen dramatically across the globe" (PMID: 34590133); "Hib was the leading cause of meningitis in children prior to the introduction of an effective vaccination" (PMID: 21999651).

Finding 2 — Pathophysiology is LOS-triggered, TNF-α/IL-1β-driven meningeal inflammation

In the rabbit model, intracisternal Hib LOS induced CSF TNF within 45 min, preceding leukocyte influx by ~75 min (peak TNF 45 ng/mL at 120 min); anti-TNF-α and anti-IL-1β reduced inflammation and the two cytokines were synergistic. "These data provide evidence for a seminal role of TNF-alpha and IL-1 beta in the initial events of meningeal inflammation" (PMID: 2373990). Dexamethasone before/with LOS inhibits CSF TNF: "DXM, when given before or with Hib LOS, inhibits CSF TNF production" (PMID: 2794062).

Finding 3 — Adjunctive dexamethasone reduces hearing loss, strongest in Hib

Cochrane meta-analysis (25 RCTs, 4,121 participants): severe hearing loss RR 0.67 (0.51–0.88), any hearing loss RR 0.74 (0.63–0.87), neurological sequelae RR 0.83 (0.69–1.00); mortality RR 0.90 (0.80–1.01, P=0.07, NS) (PMID: 20824838). Hib-specific benefit is greatest when dexamethasone is given before/with first antibiotic dose (PMID: 22789668).

Finding 4 — PRP capsule drives virulence; CNS entry is polarized barrier invasion

"Its major virulence factor is the polyribosyl ribitol phosphate (PRP) polysaccharide capsule" (PMID: 34076491). "Invasion occurs in a strongly polar fashion, since the bacteria enter the cells preferentially from the basolateral 'blood' side" (PMID: 30049648); transcytosis is a shared CNS-entry route (PMID: 20026234).

Finding 5 — Outcomes are dominated by setting and presenting severity

Pooled 5-trial analysis (2,123 children): dismal outcome in 54% (Angola), 31% (Latin America), 5% (Finland); independent predictors included study site (Angola vs Finland OR 11.91), GCS<13 (OR 4.58), seizures (OR 1.96), age <1 year (OR 1.55) (PMID: 34732790).

Finding 6 — Clinical presentation and complication frequencies

Case fatality up to 30%, ~50% of survivors with complications (PMID: 33807653); Saudi pediatric series (66% Hib): complications 26% — subdural effusion 23%, hearing loss 14%, seizure disorder 10%, developmental delay 9%, hydrocephalus 6% (PMID: 9570646); meningeal signs can be subtle early (PMID: 40509725).

Finding 7 — Infant rat is the principal in vivo model

Adult animals do not reliably develop meningitis (PMID: 10470555); infant-rat hematogenous model with anti-LPS protection (PMID: 10623558); Hib causes greater BBB penetration than E. coli K1 or GBS (PMID: 9184127).

Finding 8 — Rifampin chemoprophylaxis controls outbreaks

"The outbreak ended following rifampin prophylaxis of all community members younger than 15 years of age" (PMID: 3485275); inbreeding not a risk factor, no shared HLA haplotype.

Finding 9 — Meningitis is a leading infectious killer of young children

"meningitis, encephalitis and neonatal sepsis, collectively, [are] the second and third largest infectious killers of children under five" (PMID: 33668442).

Finding 10 — Diagnosis: LP/CSF + Gram/culture + multiplex PCR

FilmArray ME panel detects 14 pathogens including H. influenzae in ~1 h (PMID: 42679643); bacterial/fungal target sensitivity 100%, specificity 94.9%, NPV 100% vs culture (PMID: 42388946).

Finding 11 — Current global burden (GBD 2023)

"In 2023, there were 259 000 (202 000–335 000) global deaths and 2·54 million (2·20–2·93) incident cases of meningitis. Children younger than 5 years accounted for more than a third of deaths (86 600)" (PMID: 41911930); 80-year meta-analysis of case-fatality trends (PMID: 39093565).

Finding 12 — Serotype replacement: Hia now drives disease in Indigenous North American children

Alaska 2018–2022: 75% of 52 invasive Hia cases in Alaska Native children <5 in rural areas; incidence 17.8/100,000 in <5s (PMID: 40071574); "All deaths (n = 6) and long-term sequelae (n = 7) occurred in children with Hia or Hib meningitis" (PMID: 40882866); ACIP tailored PRP-OMP recommendation for AI/AN infants (PMID: 39264849).

Mechanistic Model / Interpretation

  Nasopharyngeal colonization (encapsulated H. influenzae, esp. Hib)
 │  adhesion (fimbriae, OMPs), mucosal invasion
 ▼
    BACTEREMIA  ◄── PRP capsule: resists phagocytosis + complement
 │
 ▼
   Blood–CSF / blood–brain barrier  ── polarized (basolateral) invasion +
   (choroid plexus epithelium,          transcytosis; tight-junction disruption
    brain microvascular endothelium)
 │
 ▼
CSF / subarachnoid space   ── bacterial multiplication + autolysis
 │
 ▼
LIPOOLIGOSACCHARIDE (LOS) release
 │  TLR4/CD14 → NF-κB (inferred)
 ▼
TNF-α  +  IL-1β  (synergistic)   ◄── IL-10 / dexamethasone suppress
 │  chemokines, adhesion molecules
 ▼
NEUTROPHILIC CSF PLEOCYTOSIS + BBB breakdown
 │
      ┌──────────┼───────────────────────┐
      ▼          ▼                        ▼
 Cerebral edema  Cochlear/CN-VIII     Vasculitis / thrombosis
 ↑ ICP           inflammation          → ischemia
 → ischemia      → SENSORINEURAL       → infarction
 → neuronal        HEARING LOSS
   necrosis
      │          │                        │
      └──────────┴───────────┬────────────┘
             ▼
     CLINICAL: fever, meningismus, ↓consciousness, seizures
     OUTCOME: death (≤30%); survivors ~50% sequelae
      (deafness, epilepsy, cognitive impairment, hydrocephalus)

Upstream vs downstream. The capsule and barrier invasion are upstream determinants of whether invasive disease occurs; the LOS→TNF-α/IL-1β cascade is the upstream determinant of how much injury occurs once bacteria reach the CSF. This distinction explains why the two most effective interventions act at different points: vaccination/anti-PRP antibody blocks the upstream capsule-dependent step (prevention), while dexamethasone dampens the downstream cytokine cascade (reduces sequelae, especially deafness). Antibiotics kill bacteria but, by causing bacteriolysis and LOS release, can transiently intensify the cytokine surge — the mechanistic rationale for giving dexamethasone before or with the first antibiotic dose.

Evidence Base

PMID Contribution Supports
33247582 30-yr Netherlands surveillance; conjugate-vaccine IRRs 0.02–0.04 F1 (vaccine impact)
34590133 Global dramatic Hib decline F1, prevention
21999651 Hib as pre-vaccine leading cause F1
2373990 TNF-α/IL-1β seminal role, rabbit model F2 (mechanism)
2794062 Dexamethasone suppresses LOS-induced CSF TNF F2, treatment
9359724 IL-10 counter-regulates CSF TNF Mechanism
7798656 sTNFR/IL-1RA ineffective vs LOS (redundancy) Mechanism nuance
20824838 Cochrane: dexamethasone RR 0.34 severe hearing loss in Hib F3 (treatment)
22789668 Timing of dexamethasone in Hib F3
34076491 PRP as major virulence factor F4
30049648 Polarized blood–CSF invasion (HIBCPP) F4, models
20026234 Transcytosis CNS entry F4
41318968 Tight-junction disruption mechanisms Mechanism/anatomy
15274747 vapD/vapX intracellular survival Molecular
34732790 Prognostic factors, 3-continent outcomes F5
33807653 Case fatality, complication spectrum F6
9570646 Per-complication frequencies (66% Hib cohort) F6
40509725 Subtle early meningeal signs, adult case F6
10470555 Infant-animal model rationale F7 (models)
10623558 Infant-rat model, anti-LPS protection F7
9184127 BBB permeability greater with Hib F7
1759817 Dexamethasone ↓ cochlear inflammation F7, treatment
3485275 Rifampin controls Amish outbreak F8 (prevention)
33668442 Meningitis global mortality ranking F9
42679643 FilmArray ME panel (14 pathogens, ~1h) F10 (diagnostics)
42388946 ME panel performance vs culture F10
42256222 Culture still essential (AST, coverage) F10
41911930 GBD 2023 burden estimates F11
39093565 80-yr case-fatality meta-analysis (H. flu 11%) F11, prognosis
40071574 Alaska Hia epidemiology F12
40882866 Hia/Hib drive deaths/sequelae in Alaska F12
39264849 ACIP tailored AI/AN Hib vaccine F12, prevention
34491462 a/b polysaccharide non-cross-reactivity Serotype replacement
38070126 Seroprotection, ~1 µg/mL threshold Prevention

Limitations and Knowledge Gaps

  1. Disease-level, not patient-level evidence. This report synthesizes surveillance, cohorts, RCTs, and animal/cell models. There is no host-genetic dataset — appropriately, since the disease is infectious, not heritable. Sections 4 (host genetics), 14 (natural animal disease), and pharmacogenomics are largely "not applicable."
  2. Serotype-specific data are sparse for non-b strains. Most mechanistic and much clinical data derive from Hib; the pathophysiology of Hia and nontypeable strains is assumed similar but less directly demonstrated.
  3. Corticosteroid benefit is setting-dependent. Dexamethasone benefit is robust in high-income settings but not demonstrated in low-income countries where the disease burden is highest (PMID: 20824838) — a major equity gap.
  4. Signaling detail is partly inferred. The TLR4/CD14→NF-κB step upstream of TNF-α/IL-1β is canonical/inferred; the cytokine outputs themselves are directly demonstrated in models.
  5. Model limitations. Infant-rodent and rabbit models require non-natural inoculation routes and age restriction; they may not capture all aspects of human disease, particularly adult/comorbid presentations and long-term neurocognitive sequelae.
  6. Diagnostic gaps. Multiplex PCR panels miss non-panel pathogens and cannot provide antimicrobial susceptibility; inter-platform discordance exists (PMID: 42684933). Culture remains essential.
  7. Surveillance heterogeneity. Global burden estimates differ substantially between WHO-MCEE and IHME-GBD models (PMID: 33668442), reflecting under-diagnosis in low-resource settings.

Proposed Follow-up Experiments / Actions

  1. Accelerate Hia conjugate vaccine development and evaluation, prioritizing Indigenous North American populations, given demonstrated serotype replacement, lack of a/b cross-protection, and concentrated mortality/sequelae (PMID: 34491462; PMID: 40071574; PMID: 40882866).
  2. Definitive RCTs of adjunctive dexamethasone (and alternative anti-inflammatories) in low-income, high-burden settings, since current evidence of benefit is confined to high-income countries.
  3. Strengthen molecular surveillance (serotyping + WGS) to track post-Hib serotype dynamics (a, e, f, nontypeable) and antimicrobial resistance, integrated with culture for AST.
  4. Mechanistic dissection of adjunctive host-directed therapies beyond corticosteroids (e.g., targeted modulation of the LOS→TNF-α/IL-1β axis, complement or matrix-metalloproteinase modulation) using validated infant-rat and HIBCPP barrier models, focusing on hearing-loss and neuronal-injury endpoints.
  5. Improve early recognition tools for atypical/subtle presentations (adults, subtle meningeal signs) to reduce diagnosis-to-treatment delays, which independently worsen outcome (PMID: 35419149).
  6. Standardize global burden estimation by harmonizing WHO and GBD methodologies and expanding pathogen-specific surveillance in the African meningitis belt and other high-burden regions.

Report compiled from 12 confirmed findings and 59 literature citations across 5 investigation iterations. Evidence types span human clinical cohorts/RCTs/meta-analyses, model-organism (infant rat, rabbit) studies, in-vitro barrier models, and computational/molecular-modeling work.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.3.0rc3.

Outcome Count
References checked 49
Resolved 49
Unresolved (possible confabulation) 0
Unverifiable 0
Quoted claims checked 20
Quoted claims found in source 16
Quoted claims not found in source 4
References weighed for topical relevance 49
On topic 35
Off topic 0

Quotes not found in the cited source

Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

Every one of these was searched against an abstract alone, with no full text retrieved - marked abstract only below. Where full text can be fetched, re-running with it will settle them; where the source publishes only a summary to PubMed, as GeneReviews chapters do, it will not, and the quote has to be checked by hand against the chapter itself.

  • PMID:33247582 (abstract only): "Conjugate vaccines effectively reduced the incidence of Haemophilus influenzae type b… (IRRs, .02–.04; P < .001)"
  • closest text in source: "Conjugate vaccines effectively reduced the incidence of Haemophilus influenzae type b, Neisseria meningitidis serogroup C, and 10 pneumococcal serotypes (IRRs, .02-.04; P < .001)"
  • PMID:34590133 (abstract only): "the incidence of Hib infections… has fallen dramatically across the globe"
  • closest text in source: "As a result of widespread use of the vaccines, the incidence of Hib infections, and their associated morbidity and mortality, has fallen dramatically across the globe"
  • PMID:33668442 (abstract only): "meningitis, encephalitis and neonatal sepsis, collectively, [are] the second and third largest infectious killers of children under five"
  • closest text in source: "Two models, (1) the WHO and the Johns Hopkins Bloomberg School of Public Health's Maternal and Child Epidemiology Estimation (MCEE) group's Child Mortality Estimation (WHO-MCEE) and (2) the Institute for Health Metrics and Evaluation (IHME) Global Burden of Disease Study (GBD 2017), identified meningitis, encephalitis and neonatal sepsis, collectively, to be the second and third largest infectious killers of children under five years, respectively"
  • PMID:41911930 (abstract only): "In 2023, there were 259 000 (202 000–335 000) global deaths and 2·54 million (2·20–2·93) incident cases of meningitis. Children younger than 5 years accounted for more than a third of deaths (86 600)"
  • closest text in source: "FINDINGS: In 2023, there were 259 000 (95% uncertainty interval 202 000-335 000) global deaths and 2·54 million (2·20-2·93) incident cases of meningitis"

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome Count
Terms checked 32
Resolved 32
Unresolved (possible confabulation) 0
Obsolete 0
Unverifiable 0
Terms whose name was checked 13
Terms named correctly 1
Terms named as a different term 12

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

  • HP:0001945 (1 mention) - the report calls it "Clinical sign"; HP calls it Fever
  • HP:0002315 (1 mention) - the report calls it "Symptom"; HP calls it Headache
  • HP:0031179 (1 mention) - the report calls it "Clinical sign"; HP calls it Nuchal rigidity
  • HP:0000613 (1 mention) - the report calls it "Symptom"; HP calls it Photophobia
  • HP:0001250 (1 mention) - the report calls it "Clinical sign"; HP calls it Seizure
  • HP:0000407 (1 mention) - the report calls it "Lab/clinical"; HP calls it Sensorineural hearing impairment
  • HP:0012595 (1 mention) - the report calls it "Physical/imaging"; HP calls it Mild proteinuria
  • HP:0000238 (1 mention) - the report calls it "Physical/imaging"; HP calls it Hydrocephalus
  • HP:0007360 (1 mention) - the report calls it "Clinical sign"; HP calls it Aplasia/Hypoplasia of the cerebellum
  • HP:0012229 (1 mention) - the report calls it "Lab abnormality"; HP calls it CSF pleocytosis
  • UBERON:0002361 (2 mentions) - the report calls it "Primary organ/system: central nervous system — meninges"; UBERON calls it pia mater
  • UBERON:0001844 (1 mention) - the report calls it "Secondary organ involvement / complications: inner ear/cochlea"; UBERON calls it cochlea