Chlamydophila Species - Chlamydia pneumoniae Infection

Chlamydophila is a genus of bacteria in the Chlamydiaceae family that causes atypical pneumonias, which may become life threatening. According to the CDC, the varied clinical presentation and lack of standardization for diagnostic methods available present unique challenges for accurately identifying C. pneumoniae cases and appropriately treating patients. Diagnostic laboratory tests include culture, serology, and molecular methods.

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

Background

Epidemiology

  • Incidence
    • Chlamydophila pneumophilia
    • 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

ARUP Lab Tests

Primary Tests

Detect Chlamydia pneumoniae in bronchoalveolar lavage (BAL), nasal wash, nasopharyngeal swab, or pleural fluid

Differentiate between Chlamydophila species (C. psittaci, C. pneumoniae)

Differentiate early IgM response to infection from persistent low-level titer

Because of cross-reactivity, a C. pneumoniae-specific reaction will exhibit titers two-fold or greater than C. trachomatis or C. psittaci serology

Limited value in the diagnosis of most oculogenital (eg, eyes, genitalia) chlamydial infections

Panel includes C. pneumoniae, C. trachomatis, and C. psittaci IgM titers; C. pneumoniae, C. trachomatis, and C. psittaci IgG titers

May aid in the diagnosis of Mycoplasma pneumoniae in patient with persistent pneumonia that is outside of the expected acute phase

Provide retrospective evidence of suspected Legionella pneumophila infection

Detect respiratory pathogens in patients with pneumonia

Related Tests

A combined IgG and IgM antibody panel is available

Differentiate between Chlamydophila species (C. psittaci, C. pneumoniae)

Because of cross-reactivity, a C. pneumoniae-specific reaction will exhibit titers 2-fold or greater than C. trachomatisor C. psittaci serology

Limited value in the diagnosis of most oculogenital (eg, eyes, genitalia) chlamydial infections

Panel includes C. pneumoniae, C. trachomatis, and C. psittaci IgG titers

A combined IgG and IgM antibody panel is available

Differentiate between Chlamydophila species (C. psittaci, C. pneumoniae)

Differentiate early IgM response to infection from persistent low-level titer

Because of cross-reactivity, a C. pneumoniae-specific reaction will exhibit titers 2-fold or greater than C. trachomatisor C. psittaci serology

Limited value in the diagnosis of most oculogenital (eg, eyes, genitalia) chlamydial infections

Panel includes C. pneumoniae, C. trachomatis, and C. psittaci IgM titers, and chlamydia IgM panel interpretation

Detect Mycoplasma pneumoniae bacteria

Detect Legionella species

Medical Experts

Contributor

Couturier

Marc Roger Couturier, PhD, D(ABMM)
Associate Professor of Clinical Pathology, University of Utah
Medical Director, Parasitology/Fecal Testing, Infectious Disease Antigen Testing, Bacteriology, and Molecular Amplified Detection, ARUP Laboratories
Contributor

References

Additional Resources
Resources from the ARUP Institute for Clinical and Experimental Pathology®