Chlamydophila

Snapshot

• A 26-year-old woman presents to her primary care physician for a nonproductive cough of 1-week duration. She reports that the cough started quite suddenly, along with subjective fevers. She denies having any headaches, any upper respiratory symptoms, chest pain, or shortness of breath. She has a past medical history of polycystic ovarian syndrome and anxiety. She lives at home with her parents and a 10-year-old parrot. A chest radiograph shows left lower lobe consolidation and bilateral small pleural effusions. Given her risk factors, she is started on doxycycline for suspected atypical pneumonia. (Chlamydophila psittaci infection)

Introduction

• Classification
  • Chlamydiae
    • obligate intracellular bacteria
    • Chlamydophila pneumoniae
      • atypical (interstitial) pneumonia
    • Chlamydophila psittaci
      • psittacosis, which presents as an atypical (interstitial) pneumonia or fever of unknown origin
    • Chlamydia trachomatis 
      • sexually transmitted disease, trachoma, or lymphogranuloma venereum
• Pathogenesis
  • cannot make own ATP and are obligate intracellular (Chlamys = cloak, as in cloaked inside a cell!)
  • the bacteria has 2 forms: elementary body and reticulate body
    • the elementary body (the infectious form) attaches to the outer membrane of host cells and enters through endocytosis to become intracellular
      • they produce cytoplasmic inclusions (reticulate bodies)
    • the reticulate body replicates inside the cell using fission and reorganizes into elementary bodies, which then goes on to infect more cells
• Studies
  • detection of DNA via polymerase chain reaction (PCR) or nucleic acid amplification test (NAAT)
  • detection of immunoglobulin using microimmunofluorescence
  • Giemsa stain
    • reticulate bodies seen in cytoplasm
• diagnosis is made via serologic testing and clinical findings

Chlamydophila pneumoniae

• Introduction
  • clinical syndrome
    • atypical pneumonia
    • transmission via aerosols
  • demographics
    • primarily in adolescents and young adults
    • atypical organisms uncommon in patients >65 years of age, but C. pneumoniae is the most common atypical pathogen in the elderly 
  • risk factors
    • smoking
• Presentation
  • upper respiratory symptoms (initial)
    • nasal congestion
    • sore throat
    • sinus pressure
  • pneumonia (after 1-4 weeks)
    • fever and malaise
    • cough with minimal sputum
    • hoarse voice
    • headache
    • sinus percussion tenderness
• Imaging
  • chest radiography
    • findings
      • diffuse patchy infiltrates in interstitial areas
      • generally involves more than 1 lobe
• Treatment
  • azithromycin
    • first-line
  • doxycycline
    • avoid in children and pregnant women
• Complications
  • erythema nodosum
• Guillain-Barré syndrome

Chlamydophila psittaci

• Introduction
  • clinical syndrome
    • presents as an atypical (interstitial) pneumonia or fever of unknown origin 
    • transmission via aerosols
    • reservoir is birds (parrots)
  • risk factors
    • exposure to birds, especially pet birds that are sick
    • pet shop employees
    • occupational exposure to poultry
• Presentation
  • acute onset of symptoms
  • high fever
  • nonproductive cough
  • may have splenomegaly
• Imaging
  • chest radiography
    • findings
      • unilateral single lower lobe consolidation
      • can have small pleural effusions
• Treatment
  • doxycycline or tetracycline 
    • first-line
  • azithromycin
• Complications
  • endocarditis
  • myocarditis
  • multi-organ failure