Educational resource · Not a medical device · Infectious diseases review in progress · Does not replace clinical judgement

Diagram — “Atypical” and intracellular bacteria — SeptiMap

name the atypical agents of pneumonia, explain why their diagnosis is indirect and why β-lactams fail. Educational resource, not a medical device.

Diagrams: mechanisms and principles

17 sourced diagrams · for medical students and practice

Each diagram reads step by step: an objective, the steps, three key points, a classic pitfall, its sources and the related atlas pages. Revision mode hides the labels to test yourself.

Clinical years

“Atypical” and intracellular bacteria

Objective: name the atypical agents of pneumonia, explain why their diagnosis is indirect and why β-lactams fail.

Step 5 / 5
“Atypical” and intracellular bacteria1. Three atypical agents — Mycoplasma pneumoniae, Chlamydia pneumoniae and Legionella pneumophila are the “atypical” agents of pneumonia. 2. Indirect diagnosis — Hard to culture: urinary antigen and PCR for Legionella, serology with interpretation pitfalls. 3. β-lactams fail — No wall (Mycoplasma) or intracellular life: β-lactams are inactive. 4. Active classes — Macrolides, tetracyclines and fluoroquinolones are active against these agents. 5. Other intracellular agents — Coxiella burnetii and Bartonella cause blood-culture-negative endocarditis, diagnosed by serology; Rickettsia is confirmed by paired-sera IFA serology.MycoplasmaChlamydiaLegionellano wallintracellularintracellularHard to culture: urinary antigen and PCR(Legionella), serology with cautionβ-lactams: inactive(no wall, or intracellular)Active: macrolides, tetracyclines,fluoroquinolonesOther intracellular agentsCoxiella, Bartonella: culture-negativeendocarditis → serology.Rickettsia: paired IFA serology.
  • Pathogen
  • Host (cells, tissues)
  • Antibiotic
  • Toxin, damage
  • Structure

Key points

  • Atypicals: Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella.
  • Hard to culture: urinary antigen and PCR for Legionella; interpret serology with caution.
  • β-lactams inactive; macrolides, tetracyclines, fluoroquinolones active.

Classic pitfall

Reading a raised Mycoplasma or C. pneumoniae IgG as current infection: it may reflect past exposure.

Related pathogen pages (6)

Sources

Educational content · Illustrative mechanisms · Not applicable to individual clinical decisions · MDR 2017/745

This page is the text version, generated at build time. The 3D anatomical atlas requires JavaScript.