Related Subjects:
|Chlamydophila pneumoniae
|Chlamydia psittaci
|Chlamydia trachomatis
🫁 Chlamydophila pneumoniae (formerly Chlamydia pneumoniae) is an obligate intracellular bacterium that causes
a significant proportion of community-acquired atypical pneumonias. It is spread human-to-human and may also contribute to chronic respiratory disease.
📖 About
- Important cause of atypical pneumonia worldwide, particularly in adolescents and young adults.
- May account for up to 10% of community-acquired pneumonia (CAP) cases.
- Also associated with bronchitis, pharyngitis, sinusitis, and sometimes asthma exacerbations.
🧬 Characteristics
- Obligate intracellular bacterium – requires host ATP and amino acids.
- Not well visualised on Gram stain.
- Two-phase life cycle:
- Elementary bodies (EBs): Extracellular, infectious, resistant to drying.
- Reticulate bodies (RBs): Intracellular, metabolically active, divide inside host cells.
🦠 Source
- Human-to-human transmission via respiratory droplets 💨.
- No animal reservoir (unlike Chlamydia psittaci).
🧪 Pathogenicity
- Respiratory tract infections: Pharyngitis, sinusitis, bronchitis, and pneumonia.
- Pneumonia tends to be milder than typical bacterial pneumonia, with gradual onset.
- May present with prolonged cough, hoarse voice, low-grade fever, and malaise.
- Linked to chronic diseases (e.g. asthma, COPD exacerbations, and even atherosclerosis in some studies).
🔍 Investigations
- Serology: Paired titres may help but are not very specific.
- PCR: Detects DNA and is more sensitive/specific, though not always routinely available.
- CXR: Patchy interstitial infiltrates, often lower lobe but variable.
💊 Sensitivities
- Doxycycline – highly effective (first line for adults, unless contraindicated).
- Macrolides: Azithromycin, Clarithromycin, Erythromycin – preferred in children, pregnancy, or tetracycline intolerance.
- Fluoroquinolones – sometimes effective but not first choice in UK guidelines.
🛠️ Management
- Doxycycline 100 mg BD for at least 7–10 days (adults, not in pregnancy/children).
- Azithromycin: 500 mg OD for 3 days OR 500 mg once then 250 mg OD for 4 days.
- Erythromycin: 500 mg QDS for 10–14 days (alternative if others unsuitable).
- Supportive care: rest, fluids, antipyretics as required.
📚 Key Notes
- Think of Chlamydophila pneumoniae in a patient with an atypical pneumonia, persistent cough, or hoarseness.
- Often indistinguishable clinically from Mycoplasma pneumoniae → empirical antibiotics are chosen to cover both.
- Macrolides are usually used in children, tetracyclines in adults.
