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Pneumonia caused by Chlamydia pneumoniae in adults

Dori F Zaleznik, MD
Section Editor
John G Bartlett, MD
Deputy Editor
Anna R Thorner, MD


The Chlamydia species are obligate, intracellular bacteria. Chlamydia trachomatis is a major cause of genital tract and ocular infections worldwide. The role of Chlamydia (also known as Chlamydophila) pneumoniae and less often Chlamydia psittaci in causing atypical pneumonia has become more appreciated in recent years.

Pneumonia caused by C. pneumoniae in adults will be discussed here. C. psittaci infections (psittacosis) in adults, C. pneumoniae and C. psittaci infections in children, and C. trachomatis infections are discussed separately. (See "Psittacosis" and "Pneumonia caused by Chlamydia species in children" and "Screening for sexually transmitted infections", section on 'Chlamydia and gonorrhea' and "Clinical manifestations and diagnosis of Chlamydia trachomatis infections" and "Treatment of Chlamydia trachomatis infection".)


Chlamydia species are unusual bacteria in a number of ways. The genome of the organisms is only 660 million daltons, smaller than any other prokaryote except Mycoplasma spp. They do not contain a peptidoglycan in the cell wall. The growth cycle of the organism is complex and biphasic, consisting of two distinct entities: elementary (EB) and reticulate bodies (RB) [1].

The form in which the bacterium multiplies is the RB, which is intracellular. Replication occurs within a membrane-bound inclusion. RB are unstable and revert to EB within the inclusion, which then ruptures causing release of EB, the form that survives in the extracellular environment; EB are the infectious particles.

The signal that triggers RB to EB reversion is not known. EB attach to epithelial cells and enter cells via a phagosome. Once inside, EB reorganize to RB, which then replicate.


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Literature review current through: Sep 2016. | This topic last updated: May 3, 2016.
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  1. Stamm WE, Jones RB, Batteiger BE. Introduction to Chlamydial diseases. In: Principles and Practice of Infectious Diseases, 6th edition, Mandell GL, Bennett JE, Dolin R (Eds), Churchill Livingstone, Philadelphia 2005. p.2236.
  2. Shirai M, Hirakawa H, Kimoto M, et al. Comparison of whole genome sequences of Chlamydia pneumoniae J138 from Japan and CWL029 from USA. Nucleic Acids Res 2000; 28:2311.
  3. Shirai M, Hirakawa H, Ouchi K, et al. Comparison of outer membrane protein genes omp and pmp in the whole genome sequences of Chlamydia pneumoniae isolates from Japan and the United States. J Infect Dis 2000; 181 Suppl 3:S524.
  4. Morrison RP, Manning DS, Caldwell HD. Immunology of Chlamydia trachomatis infections. In: Sexually Transmitted Diseases, Quinn TC (Ed), 1992. p.57.
  5. Emre U, Roblin PM, Gelling M, et al. The association of Chlamydia pneumoniae infection and reactive airway disease in children. Arch Pediatr Adolesc Med 1994; 148:727.
  6. Emre U, Sokolovskaya N, Roblin PM, et al. Detection of anti-Chlamydia pneumoniae IgE in children with reactive airway disease. J Infect Dis 1995; 172:265.
  7. Johansson N, Kalin M, Tiveljung-Lindell A, et al. Etiology of community-acquired pneumonia: increased microbiological yield with new diagnostic methods. Clin Infect Dis 2010; 50:202.
  8. Shibli F, Chazan B, Nitzan O, et al. Etiology of community-acquired pneumonia in hospitalized patients in northern Israel. Isr Med Assoc J 2010; 12:477.
  9. Song JH, Oh WS, Kang CI, et al. Epidemiology and clinical outcomes of community-acquired pneumonia in adult patients in Asian countries: a prospective study by the Asian network for surveillance of resistant pathogens. Int J Antimicrob Agents 2008; 31:107.
  10. Cillóniz C, Ewig S, Polverino E, et al. Microbial aetiology of community-acquired pneumonia and its relation to severity. Thorax 2011; 66:340.
  11. Kumar S, Hammerschlag MR. Acute respiratory infection due to Chlamydia pneumoniae: current status of diagnostic methods. Clin Infect Dis 2007; 44:568.
  12. Marrie TJ, Peeling RW, Fine MJ, et al. Ambulatory patients with community-acquired pneumonia: the frequency of atypical agents and clinical course. Am J Med 1996; 101:508.
  13. Gadsby NJ, Russell CD, McHugh MP, et al. Comprehensive Molecular Testing for Respiratory Pathogens in Community-Acquired Pneumonia. Clin Infect Dis 2016; 62:817.
  14. Jain S, Self WH, Wunderink RG, et al. Community-Acquired Pneumonia Requiring Hospitalization among U.S. Adults. N Engl J Med 2015; 373:415.
  15. Myhra W, Mordhorst CH, Wang SP, et al. Clinical features of Chlamydia pneumoniae, strain TWAR, infection in Denmark 1975-1987. In: Chlamydial Infections, Bowie WR, Caldwell HD, Jones RP (Eds), 1980. p.422.
  16. Janssens JP. Pneumonia in the elderly (geriatric) population. Curr Opin Pulm Med 2005; 11:226.
  17. Coon RG, Balansay MS, Faix DJ, et al. Chlamydophila pneumoniae infection among Basic Underwater Demolition/SEAL (BUD/S) candidates, Coronado, California, July 2008. Mil Med 2011; 176:320.
  18. Oktem IM, Ellidokuz H, Sevinc C, et al. PCR and serology were effective for identifying Chlamydophila pneumoniae in a lower respiratory infection outbreak among military recruits. Jpn J Infect Dis 2007; 60:97.
  19. Conklin L, Adjemian J, Loo J, et al. Investigation of a Chlamydia pneumoniae outbreak in a Federal correctional facility in Texas. Clin Infect Dis 2013; 57:639.
  20. Chirgwin K, Roblin PM, Gelling M, et al. Infection with Chlamydia pneumoniae in Brooklyn. J Infect Dis 1991; 163:757.
  21. Grayston JT, Aldous MB, Easton A, et al. Evidence that Chlamydia pneumoniae causes pneumonia and bronchitis. J Infect Dis 1993; 168:1231.
  22. Miyashita N, Niki Y, Nakajima M, et al. Prevalence of asymptomatic infection with Chlamydia pneumoniae in subjectively healthy adults. Chest 2001; 119:1416.
  23. Bourke SJ, Lightfoot NF. Chlamydia pneumoniae: defining the clinical spectrum of infection requires precise laboratory diagnosis. Thorax 1995; 50 Suppl 1:S43.
  24. Kauppinen MT, Lähde S, Syrjälä H. Roentgenographic findings of pneumonia caused by Chlamydia pneumoniae. A comparison with streptococcus pneumonia. Arch Intern Med 1996; 156:1851.
  25. Gaydos CA, Roblin PM, Hammerschlag MR, et al. Diagnostic utility of PCR-enzyme immunoassay, culture, and serology for detection of Chlamydia pneumoniae in symptomatic and asymptomatic patients. J Clin Microbiol 1994; 32:903.
  26. US Food and Drug Administration (FDA) News Release. FDA expands use for FilmArray Respiratory Panel. http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm304177.htm (Accessed on June 11, 2012).
  27. Idaho Technology Inc. The FilmArray Respiratory Panels. http://www.idahotech.com/FilmArray/RespiratoryTest.html (Accessed on June 11, 2012).
  28. Idaho Technology Inc. FilmArray Respiratory Panel - Information Sheet. http://www.idahotech.com/pdfs/FilmArray/InfoSheet,%20FilmArray%20Respiratory%20Panel-0229.pdf (Accessed on June 11, 2012).
  29. Tuuminen T, Palomäki P, Paavonen J. The use of serologic tests for the diagnosis of chlamydial infections. J Microbiol Methods 2000; 42:265.
  30. Vergis EN, Indorf A, File TM Jr, et al. Azithromycin vs cefuroxime plus erythromycin for empirical treatment of community-acquired pneumonia in hospitalized patients: a prospective, randomized, multicenter trial. Arch Intern Med 2000; 160:1294.
  31. Siegel JD, Rhinehart E, Jackson M, et al. Healthcare Infection Control Practices Advisory Committee 2007 Guideline for Isolation Precautions: Preventing Transmission of Infectious Agents in Healthcare Settings, June 2007 http://www.cdc.gov/ncidod/dhqp/gl_isolation.html (Accessed on December 06, 2011).