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
- 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
- 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
- Chlamydophila pneumophilia
- 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
- Chlamydophila pneumoniae – peak incidence is late childhood to young adulthood
- 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
- C. pneumoniae – respiratory secretions
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 Laboratory Tests
Detect Chlamydia pneumoniae in bronchoalveolar lavage (BAL), nasal wash, nasopharyngeal swab, or pleural fluid
Qualitative Polymerase Chain Reaction
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
Semi-Quantitative Indirect Fluorescent Antibody
May aid in the diagnosis of Mycoplasma pneumoniae in patient with persistent pneumonia that is outside of the expected acute phase
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Provide retrospective evidence of suspected Legionella pneumophila infection
Qualitative Enzyme-Linked Immunosorbent Assay
Detect respiratory pathogens in patients with pneumonia
Massively Parallel Sequencing
Automated Cell Count/Differential
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
Semi-Quantitative Indirect Fluorescent Antibody
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
Semi-Quantitative Indirect Fluorescent Antibody
Panel includes C. pneumoniae, C. trachomatis, and C. psittaci IgM titers, and chlamydia IgM panel interpretation
Detect Mycoplasma pneumoniae bacteria
Qualitative Polymerase Chain Reaction
Detect Legionella species
Qualitative Polymerase Chain Reaction
Medical Experts
Couturier

Hillyard

References
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Mandell LA, Wunderink RG, Anzueto A, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. 2007;44 Suppl 2:S27-72.
20724512
17868919
24828565
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Paul L, Comstock J, Edes K, Schlaberg R. Gestational Psittacosis Resulting in Neonatal Death Identified by Next-Generation RNA Sequencing of Postmortem, Formalin-Fixed Lung Tissue. Open Forum Infect Dis. 2018;5(8):ofy172.
Panel includes C. pneumoniae, C. trachomatis, and C. psittaci IgM titers; C. pneumoniae, C. trachomatis, and C. psittaci IgG titers