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For further information, see CMDT Part 33-38: Infections Caused by Chlamydiae

Key Features

  • Chlamydophila pneumoniae (formerly known as Chlamydia pneumoniae) causes pneumonia and bronchitis

  • C pneumoniae causes approximately 10% of community-acquired pneumonias

  • C pneumoniae is second only to Mycoplasma as an agent of atypical pneumonia

Clinical Findings

  • The clinical presentation is that of an atypical pneumonia


  • Microimmunofluorescence or complement fixation test of acute and convalescent sera


  • Strains of C pneumoniae are resistant to sulfonamides

  • Azithromycin (500 mg orally on day 1 and 250 mg daily for days 2–5) or doxycycline (100 mg orally two times a day for 10 days) appears to be effective therapy

  • Fluoroquinolones, such as levofloxacin (500 mg orally once daily for 7–14 days) or moxifloxacin (400 mg orally once daily for 7–14 days), are active in vitro against C pneumoniae and probably are effective

  • It is unclear if empiric coverage for atypical pathogens in hospitalized patients with community-acquired pneumonia provides a survival benefit or improves clinical outcome

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