Mycoplasma Pneumoniae Pneumonia

name: Mycoplasma Pneumoniae Pneumonia
creation_date: "2026-06-28T00:00:00Z"
description: >
  Mycoplasma pneumoniae pneumonia is an atypical ("walking") pneumonia caused by
  Mycoplasma pneumoniae, a leading cause of community-acquired pneumonia in
  school-aged children and young adults. M. pneumoniae adheres to and damages the
  respiratory epithelium and characteristically lacks a bacterial cell wall, which
  makes it intrinsically resistant to beta-lactam antibiotics and dictates
  treatment with protein-synthesis inhibitors (macrolides, tetracyclines) or
  fluoroquinolones. Acquired macrolide resistance is an increasing problem.
category: Infectious Disease
parents:
- Bacterial Respiratory Infection
synonyms:
- Mycoplasma pneumonia
- Atypical pneumonia (Mycoplasma)
- Walking pneumonia
disease_term:
  preferred_term: Mycoplasma pneumoniae pneumonia
  term:
    id: MONDO:0005867
    label: Mycoplasma pneumoniae pneumonia
pathophysiology:
- name: Airway Epithelial Adherence and Atypical Pneumonia
  role: trigger
  description: >
    M. pneumoniae attaches to the respiratory epithelium via specialized adhesins
    and damages the airway surface, producing an atypical pneumonia. It is a
    leading cause of community-acquired pneumonia in school-aged children and young
    adults, often with a protracted, relatively mild ("walking") course.
  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
  - 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:39475213
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Mycoplasma pneumoniae is a leading cause of community-acquired pneumonia
      among school-aged children and young adults.
    explanation: >-
      Establishes M. pneumoniae as a leading cause of community-acquired pneumonia
      in children and young adults. Evidence source is OTHER as this is a review
      article.
  downstream:
  - target: Cell-Wall Deficiency and Intrinsic Beta-Lactam Resistance
    description: >-
      The organism's lack of a cell wall removes the beta-lactam target,
      determining antibiotic selection.
  - target: Bacterial Ribosomal Translation (Macrolide Target)
    description: >-
      Treatment instead targets bacterial ribosomal protein synthesis.

- name: Cell-Wall Deficiency and Intrinsic Beta-Lactam Resistance
  role: intrinsic_resistance
  conforms_to: "bacterial_cell_wall_synthesis_inhibition#Intrinsic Resistance in Cell-Wall-Deficient Organisms"
  description: >
    M. pneumoniae has no peptidoglycan cell wall, so the penicillin-binding-protein
    target of beta-lactam antibiotics does not exist. The organism is therefore
    intrinsically resistant to beta-lactams, which is why cell-wall-active drugs
    are useless and treatment relies on agents that act on other targets.
  biological_processes:
  - preferred_term: response to antibiotic
    term:
      id: GO:0046677
      label: response to antibiotic
  evidence:
  - reference: PMID:39475213
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The lack of a cell wall and reduced metabolic pathways limit the options for
      antibiotic treatment.
    explanation: >-
      States that M. pneumoniae's lack of a cell wall limits antibiotic options,
      the intrinsic-resistance principle this node represents. Evidence source is
      OTHER as this is a review article.
  - reference: PMID:34750083
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      most atypical pathogens do not have a bacterial cell wall, some are
      intracellular (e.g., Legionella), and some are paracellular (e.g., M.
      pneumoniae)
    explanation: >-
      Confirms M. pneumoniae lacks a bacterial cell wall, removing the beta-lactam
      target. Evidence source is OTHER as this is a review article.
  downstream: []

- name: Bacterial Ribosomal Translation (Macrolide Target)
  role: therapeutic_vulnerability
  conforms_to: "bacterial_protein_synthesis_inhibition#Bacterial mRNA Translation by the Ribosome"
  description: >
    Lacking a cell-wall target, M. pneumoniae is treated with antibiotics that act
    on its 70S ribosome. Macrolides (e.g., azithromycin) bind the 50S ribosomal
    subunit and block bacterial protein synthesis — the molecular target that makes
    a macrolide, rather than a beta-lactam, first-line therapy.
  biological_processes:
  - preferred_term: translation
    term:
      id: GO:0006412
      label: translation
  evidence:
  - reference: PMID:24336183
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The ribosome is one of the main antibiotic targets in the bacterial cell.
    explanation: >-
      Establishes the bacterial ribosome as the target of macrolides and other
      protein-synthesis inhibitors, the step this node represents. Evidence source
      is OTHER as this is a review article.
  downstream:
  - target: Acquired Macrolide Resistance
    description: >-
      Mutations at the ribosomal macrolide-binding site confer acquired resistance.

- name: Acquired Macrolide Resistance
  role: adaptive_escape
  conforms_to: "bacterial_protein_synthesis_inhibition#Ribosomal Target Resistance"
  description: >
    Acquired macrolide resistance, driven by mutations in the 23S rRNA
    macrolide-binding site, is an increasing problem in M. pneumoniae and can
    necessitate switching to a tetracycline or fluoroquinolone.
  biological_processes:
  - preferred_term: response to antibiotic
    term:
      id: GO:0046677
      label: response to antibiotic
  evidence:
  - reference: PMID:39475213
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Acquired macrolide resistance is a growing concern, with >80% of cases in
      China being macrolide-resistant.
    explanation: >-
      Documents acquired macrolide resistance as a growing concern, the
      ribosomal-target-resistance escape this node represents. Evidence source is
      OTHER as this is a review article.
  downstream: []
phenotypes:
- category: Respiratory
  name: Atypical Pneumonia
  description: >
    Community-acquired atypical pneumonia, typically with a protracted, relatively
    mild ("walking") course.
  phenotype_term:
    preferred_term: Pneumonia
    term:
      id: HP:0002090
      label: Pneumonia
  evidence:
  - reference: PMID:39475213
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Mycoplasma pneumoniae is a leading cause of community-acquired pneumonia
      among school-aged children and young adults.
    explanation: >-
      Supports community-acquired pneumonia as the defining manifestation.
      Evidence source is OTHER as this is a review article.
- category: Respiratory
  name: Cough
  description: >
    A persistent, often dry cough is the hallmark symptom of M. pneumoniae
    infection.
  phenotype_term:
    preferred_term: Cough
    term:
      id: HP:0012735
      label: Cough
- category: Constitutional
  name: Fever
  description: >
    Fever commonly accompanies acute M. pneumoniae infection.
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
treatments:
- name: Azithromycin
  description: >
    Macrolide antibiotic that inhibits bacterial protein synthesis at the 50S
    ribosomal subunit; first-line therapy for M. pneumoniae because the organism
    has no cell wall for beta-lactams to target. Empiric choice should account for
    rising macrolide resistance.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: azithromycin
      term:
        id: CHEBI:2955
        label: azithromycin
  target_mechanisms:
  - target: Bacterial Ribosomal Translation (Macrolide Target)
    treatment_effect: INHIBITS
    description: >-
      Azithromycin binds the 50S ribosome and arrests bacterial protein synthesis,
      the molecular target that makes a macrolide first-line for cell-wall-less
      M. pneumoniae.
  - target: Airway Epithelial Adherence and Atypical Pneumonia
    treatment_effect: INHIBITS
    description: >-
      By halting protein synthesis, azithromycin clears the organism from the
      airway and resolves the atypical pneumonia.
notes: >
  Created as part of the Respiratory Infections project. Worked conformer for the
  bacterial_cell_wall_synthesis_inhibition module's intrinsic-resistance branch
  (cell-wall-deficient organism) and for the bacterial_protein_synthesis_inhibition
  module (ribosomal target + acquired macrolide resistance). The infectious_agent
  (NCBITaxon) block was omitted at creation and the organism is described in the
  text.