Chlamydophila Species - Chlamydia pneumoniae Infection

Diagnosis

Indications for Testing

• Chlamydophila pneumoniae – atypical pneumonia presentation
• Chlamydophila psittaci – atypical pneumonia and history of bird exposure

Laboratory Testing

• Chlamydophila pneumoniae infection (CDC, 2016)
• Psittacosis (CDC, 2016)
• Initial testing – CBC with differential
• Polymerase chain reaction (PCR) – much more sensitive than culture and serology
• Serology – atypical pneumonia presentation
  • Order C. pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila concurrently; routine diagnostic tests to identify etiologic agent of outpatient pneumonia in adults are optional (Mandell, Infectious Disease Society of America/American Thoracic Society, 2007)
  • Confirmed by paired serology for C. pneumoniae (four-fold elevation)
• Culture
  • Difficult to grow atypical agents; positive culture confirms diagnosis
  • Suspicion for C. psittaci
    • Order antibody panel
    • Performed using complement fixation, microimmunofluorescence, enzyme immunoassay

Imaging Studies

Chest x-ray – no distinctive chest x-ray pattern

Differential Diagnosis

• Respiratory tract infections
  • M. pneumoniae
  • L. pneumophila
  • Coxiella burnetii (Q-fever)
  • Influenza virus
  • Parainfluenza 1, 2, 3, 4
  • Hantavirus
  • Respiratory syncytial virus (RSV)
  • Bordetella pertussis (whooping cough)
  • Adenovirus
• Hepatitis – viral
• Myocarditis
• Myocardial infarction
• Connective tissue disease
  • Polymyositis
• Erythema nodosum/erythema multiforme

Background

Epidemiology

• Incidence
  • Chlamydophila pneumophilia
    • Overall incidence unknown (CDC, 2015) 
    • ~7-10% of community-acquired pneumonias in adults
  • Chlamydophila psittaci – rare in U.S.; zoonotic disease
• Age
  • Chlamydophila pneumoniae – peak incidence is late childhood to young adulthood
    • ~50% of young adults in the U.S. will have evidence of past infection by age 20
    • Reinfection throughout life is common
• Transmission
  • C. pneumoniae – respiratory secretions
    • May produce epidemics in close-quarter settings such as military barracks, prisons
  • C. psittaci – respiratory inhalation of dried secretions during exposure to infected birds
    • Does not require prolonged contact with infected bird
    • May be an occupation-related disease

Organism

 C. pneumoniae and C. psittaci are obligate, intracellular, gram-negative bacteria

Clinical Presentation

• C. pneumoniae
  • Incubation – 7-10 days
  • Constitutional – leukocytosis and fever are often lacking; may resemble Mycoplasma pneumoniae infections
  • Pulmonary – cough, bronchitis, pneumonia, exacerbations of chronic bronchitis and asthma
  • Upper respiratory tract – laryngitis, otitis media, sinusitis, pharyngitis
  • Dermatologic – erythema nodosum
  • Neurologic – meningitis (uncommon)
  • Cardiac – endocarditis, myocarditis (uncommon)
• C. psittaci
  • Incubation – 5-19 days
  • Constitutional – fever, chills, headache, myalgias
  • Pulmonary – dry cough, pleural rub, rales, dyspnea, pneumonia
  • Gastrointestinal – diarrhea, nausea, anorexia, abdominal pain
  • Hepatitic – hepatitis
  • Dermatologic – faint macular rash may occur (Horder spots), erythema multiforme, erythema nodosum
  • Neurologic – cranial nerve palsies, cerebellar involvement, transverse myelitis, meningitis
  • Cardiac – endocarditis, myocarditis, pericarditis