Pneumococcal Pneumonia

name: Pneumococcal Pneumonia
creation_date: "2026-06-28T00:00:00Z"
description: >
  Pneumococcal pneumonia is community-acquired pneumonia caused by Streptococcus
  pneumoniae, the most common bacterial cause of community-acquired pneumonia,
  particularly among hospitalized patients. After nasopharyngeal colonization, the
  encapsulated organism invades the lower respiratory tract and produces a typical
  lobar pneumonia. As a classic cell-walled (Gram-positive) bacterium, it is
  treated with beta-lactam antibiotics that target the penicillin-binding-protein
  transpeptidases — the diametric opposite of cell-wall-deficient atypical
  pathogens such as Mycoplasma. Acquired penicillin resistance via altered
  penicillin-binding proteins is widespread, and conjugate vaccines have reduced
  invasive pneumococcal disease.
category: Infectious Disease
parents:
- Bacterial Respiratory Infection
synonyms:
- Streptococcus pneumoniae pneumonia
- Pneumococcal community-acquired pneumonia
disease_term:
  preferred_term: pneumococcal pneumonia
  term:
    id: MONDO:0005114
    label: pneumococcal infection
pathophysiology:
- name: Pneumococcal Colonization and Lower Airway Invasion
  role: trigger
  description: >
    Streptococcus pneumoniae colonizes the nasopharynx and, in susceptible hosts,
    invades the lower respiratory tract. It remains the most common bacterial cause
    of community-acquired pneumonia, especially among patients requiring
    hospitalization. This colonizing/invading organism is the proximal event from
    which the lobar pneumonia and the antibiotic-target biology follow.
  cell_types:
  - preferred_term: respiratory epithelial cell
    term:
      id: CL:0002632
      label: epithelial cell of lower respiratory tract
  biological_processes:
  - preferred_term: adhesion of symbiont to host
    term:
      id: GO:0044406
      label: adhesion of symbiont to host
  evidence:
  - reference: PMID:42203421
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Although Streptococcus pneumoniae remains the most common bacterial cause of
      CAP, particularly among patients requiring hospitalization, its frequency has
      declined.
    explanation: >-
      Establishes S. pneumoniae as the most common bacterial cause of
      community-acquired pneumonia. Evidence source is OTHER as this is a review
      article.
  downstream:
  - target: Lobar Pneumonia
    description: >-
      Lower-airway invasion produces a typical lobar pneumonia.
  - target: Penicillin-Binding Protein Transpeptidase (Beta-Lactam Target)
    description: >-
      The organism's cell-wall cross-linking enzymes are the target of beta-lactam
      therapy.

- name: Lobar Pneumonia
  role: consequence
  description: >
    Invasion of the alveolar spaces produces a typical lobar pneumonia with
    consolidation, fever, productive cough, and dyspnea; bacteremia and
    parapneumonic effusion may complicate severe disease.
  biological_processes:
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  locations:
  - preferred_term: lung
    term:
      id: UBERON:0002048
      label: lung
  evidence:
  - reference: PMID:42203421
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Although Streptococcus pneumoniae remains the most common bacterial cause of
      CAP, particularly among patients requiring hospitalization, its frequency has
      declined.
    explanation: >-
      Supports pneumococcal pneumonia as a leading form of community-acquired
      pneumonia, especially in hospitalized patients. Evidence source is OTHER as
      this is a review article.
  downstream: []

- name: Penicillin-Binding Protein Transpeptidase (Beta-Lactam Target)
  role: therapeutic_vulnerability
  conforms_to: "bacterial_cell_wall_synthesis_inhibition#Peptidoglycan Cross-Linking by Penicillin-Binding Proteins"
  description: >
    As a cell-walled Gram-positive bacterium, S. pneumoniae depends on
    penicillin-binding-protein (PBP) transpeptidases to cross-link peptidoglycan.
    Beta-lactam antibiotics (penicillins, cephalosporins) acylate these PBPs and
    abolish transpeptidation, making them the mainstay of therapy — in direct
    contrast to cell-wall-deficient atypical pathogens that lack this target.
  biological_processes:
  - preferred_term: peptidoglycan-based cell wall biogenesis
    term:
      id: GO:0009273
      label: peptidoglycan-based cell wall biogenesis
  evidence:
  - reference: PMID:22203377
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      although glycan chain polymerization occurs in the absence of
      transpeptidation (for example, in the presence of penicillin), efficient
      transpeptidation requires ongoing GTase reactions
    explanation: >-
      States that penicillin abolishes transpeptidation (the PBP cross-linking
      reaction), confirming this node as the beta-lactam target. Evidence source is
      OTHER as this is a review article.
  downstream:
  - target: Acquired Penicillin Resistance via Altered PBPs
    description: >-
      Pneumococci escape beta-lactams by remodeling the PBP target.

- name: Acquired Penicillin Resistance via Altered PBPs
  role: adaptive_escape
  conforms_to: "bacterial_cell_wall_synthesis_inhibition#Acquired Resistance and Drug Inactivation"
  description: >
    Penicillin resistance in pneumococci arises chiefly through mosaic
    penicillin-binding proteins with reduced beta-lactam affinity, and resistance to
    macrolides and other alternatives is widespread, complicating empirical therapy.
  biological_processes:
  - preferred_term: response to antibiotic
    term:
      id: GO:0046677
      label: response to antibiotic
  evidence:
  - reference: PMID:38667036
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Resistance to major alternatives of penicillins, macrolides, and lincosamides
      has become widespread among pneumococci and streptococci, especially in Asia
    explanation: >-
      Documents widespread resistance among pneumococci to penicillins and major
      alternatives. Evidence source is OTHER as this is a review article.
  downstream: []
phenotypes:
- category: Respiratory
  name: Pneumonia
  description: >
    Typical lobar community-acquired pneumonia is the defining manifestation.
  phenotype_term:
    preferred_term: Pneumonia
    term:
      id: HP:0002090
      label: Pneumonia
  evidence:
  - reference: PMID:42203421
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Although Streptococcus pneumoniae remains the most common bacterial cause of
      CAP, particularly among patients requiring hospitalization, its frequency has
      declined.
    explanation: >-
      Supports pneumococcal pneumonia (community-acquired pneumonia) as the defining
      manifestation. Evidence source is OTHER as this is a review article.
- category: Constitutional
  name: Fever
  description: >
    High fever is typical of acute pneumococcal pneumonia.
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
- category: Respiratory
  name: Cough
  description: >
    Productive cough is a cardinal symptom.
  phenotype_term:
    preferred_term: Cough
    term:
      id: HP:0012735
      label: Cough
- category: Respiratory
  name: Dyspnea
  description: >
    Shortness of breath reflects alveolar consolidation.
  phenotype_term:
    preferred_term: Dyspnea
    term:
      id: HP:0002094
      label: Dyspnea
treatments:
- name: Beta-Lactam Antibiotic Therapy
  description: >
    Penicillins (and cephalosporins such as ceftriaxone) acylate pneumococcal
    penicillin-binding-protein transpeptidases, blocking peptidoglycan cross-linking;
    they are the mainstay of therapy, with agent choice guided by local penicillin
    resistance.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: benzylpenicillin (penicillin G)
      term:
        id: CHEBI:18208
        label: benzylpenicillin
  target_mechanisms:
  - target: Penicillin-Binding Protein Transpeptidase (Beta-Lactam Target)
    treatment_effect: INHIBITS
    description: >-
      Beta-lactams acylate the PBP transpeptidases and abolish peptidoglycan
      cross-linking, killing the organism.
- name: Pneumococcal Vaccination
  description: >
    Pneumococcal conjugate and polysaccharide vaccines reduce invasive pneumococcal
    disease and have contributed to the declining frequency of pneumococcal CAP.
  treatment_term:
    preferred_term: vaccination
    term:
      id: MAXO:0001017
      label: vaccination
  evidence:
  - reference: PMID:42203421
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Several factors likely contribute to the evolving etiology of CAP, including
      vaccination programs, pandemics, and changes in host immunity.
    explanation: >-
      Supports vaccination programs as a driver of the declining frequency of
      pneumococcal CAP. Evidence source is OTHER as this is a review article.
notes: >
  Created as part of the Respiratory Infections project. The deliberate
  cell-walled (typical-pneumonia) counterpart to Mycoplasma_Pneumoniae_Pneumonia:
  conforms to the bacterial_cell_wall_synthesis_inhibition module's PBP
  cross-linking (beta-lactam target) and acquired-resistance nodes. disease_term
  uses MONDO:0005114 (pneumococcal infection) with a more specific preferred_term
  because MONDO lacks a dedicated "pneumococcal pneumonia" term. The
  infectious_agent (NCBITaxon) block was omitted at creation and S. pneumoniae is
  described in the text.