Chlamydophila pneumoniae or psittaci

Dx
Background
Lab Tests

Diagnosis

Indications for Testing

C. pneumoniae – atypical pneumonia presentation
C. psittaci – atypical pneumonia and history of bird exposure

Laboratory Testing

Initial testing – CBC with differential
Serology
- Order C. pneumoniae, M. pneumoniae and Legionella pneumophila concurrently; routine diagnostic tests to identify etiologic agent of outpatient pneumonia in adults is optional (Infectious Disease Society of America/American Thoracic Society)
- Confirmed by paired serology for C. pneumoniae (four-fold elevation)
- Order antibody panel if suspicious of C. psittaci
- Performed using complement fixation, microimmunofluorescence, enzyme immunoassay
PCR – much more sensitive than culture and serology
Culture – difficult on atypical agents; positive culture confirms diagnosis

Imaging Studies

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

Differential Diagnosis

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

Clinical Background

Chlamydophila is a genus of bacteria in the Chlamydiaceae family that causes atypical pneumonias, which may become life threatening.

Epidemiology

Incidence – C. pneumophilia – 100/100,000 in U.S.
- 7-10% of community-acquired pneumonias in adults
Age
- C. 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
- C. psittaci – respiratory inhalation during exposure to infected birds (zoonoses)
  - Does not require prolonged contact with infected bird
  - May be an occupation-related disease

Organism

C. psittaci and C. pneumoniae 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 – 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 – 7-14 days
- Constitutional – fever, chills, headache, myalgias
- Pulmonary – 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

Treatment

Antibiotic treatment is effective and curative

Indications for Laboratory Testing

Tests generally appear in the order most useful for common clinical situations
Click on number for test-specific information in the ARUP Laboratory Test Directory

Test Name and Number	Recommended Use	Limitations	Follow Up
CBC with Platelet Count and Automated Differential 0040003 Method: Automated Cell Count/Differential	May help differentiate between bacterial and viral pneumonias
Chlamydia pneumoniae by PCR 0060715 Method: Qualitative Polymerase Chain Reaction	Confirm C. pneumoniae as infectious agent in nasal wash, nasopharyngeal aspirate, bronchoalveolar lavage (BAL) or pleural fluid More sensitive than IFA and culture
Chlamydia Antibody Panel, IgG & IgM by IFA 0065100 Method: Semi-Quantitative Indirect Fluorescent Antibody	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	Anti-chlamydial IgM antibody is very cross-reactive and will often represent titers to multiple, non-infecting chlamydial species	If results are equivocal, retest sera 2-3 weeks after first test
Mycoplasma pneumoniae Antibodies Seroconversion Panel, IgG & IgM 0050697 Method: Semi-Quantitative Enzyme Immunoassay	Testing to evaluate for acute Chlamydia infection Because of cross-reactivity, a C. pneumoniae-specific reaction will exhibit titers two-fold or greater than C. trachomatis or C. psittaci serology
Legionella pneumophila Antigen, Urine 0070322 Method: Qualitative Enzyme-Linked Immunosorbent Assay	Rapid diagnostic test for Legionella

Additional Tests Available

Click the plus sign to expand the table of additional tests.

Test Name and Number	Comments
Chlamydia Antibody Panel, IgG by IFA 0065139 Method: Semi-Quantitative Indirect Fluorescent Antibody
Chlamydia Antibody Panel, IgM by IFA 0065105 Method: Semi-Quantitative Indirect Fluorescent Antibody
Mycoplasma pneumoniae by PCR 0060256 Method: Qualitative Polymerase Chain Reaction	Evaluate for Chlamydia infection
Legionella Species by PCR 0056105 Method: Qualitative Polymerase Chain Reaction	Rapid diagnostic test for Legionella, particularly in patient partially treated with empirical antibiotics