Clinical Overview of Chlamydia pneumoniae Infection

Key points

  • Chlamydia pneumoniae infect the upper or lower respiratory tract.
  • Most respiratory infections caused by C. pneumoniae are asymptomatic or mild.
  • Illness is usually self-limiting, but treatment with antibiotics is sometimes recommended.
  • Clinical reference laboratories can provide diagnostic testing for C. pneumoniae infections.
A healthcare provider listens to a man's breathing through a stethoscope

Cause

C. pneumoniae are a type of bacteria that can cause respiratory tract infections. These bacteria were previously called Chlamydophila pneumoniae.

C. pneumoniae have a unique developmental cycle with growth taking place within host cells (see image below). Culturing the bacteria requires growth within eukaryotic cells rather than on cell-free culture media.

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An illustration of how C. pneumoniae growth consists of two alternating forms: elementary and reticulate bodies.
C. pneumoniae form elementary and reticulate bodies (EB and RB).
SOURCE:

Reprinted by permission from Macmillan Publishers Ltd: https://doi.org/10.1038/nrmicro1007.

Who is at risk

Primary infection occurs mainly in school-aged children or young adults.

Reinfection is most common in older adults.

Incubation period

C. pneumoniae infection generally has a long incubation period of 3 to 4 weeks. However, studies have documented shorter times.

How it spreads

C. pneumoniae usually spread from close person-to-person contact by respiratory droplets.

C. pneumoniae can also spread through fomites. This happens when people touch surfaces contaminated with those respiratory droplets and then touch their nose or mouth.

Infection rates

There is no national reporting or surveillance system for C. pneumoniae infections. It's likely that many C. pneumoniae infections aren't identified due to it usually only causing mild or no symptoms.

Keep Reading: Surveillance and Trends

Risk of death

Risk of death is low, but not zero. Severe complications can occur with C. pneumoniae infections. These complications can result in hospitalization and sometimes death.

Clinical features

Most respiratory infections caused by C. pneumoniae are asymptomatic or mild.

Keep Reading: Clinical Features

Testing and diagnosis

When to collect specimens‎

Collect specimens before antimicrobial therapy starts, if possible. Culture and molecular test methods are more likely to detect C. pneumoniae when specimen collection occurs before antimicrobial therapy starts.
Learn about specimen collection protocol

Clinical reference laboratories can provide diagnostic testing for C. pneumoniae infections using

  • Culture
  • Serology
  • Molecular methods

There are multiple commercially available systems for the direct detection of C. pneumoniae in respiratory specimens. This includes several Food and Drug Administration-cleared tests.

Keep Reading: Laboratory Testing

Treatment and recovery

Illness caused by C. pneumoniae is usually self-limiting and people may not seek care.

Healthcare providers can treat the disease on a case-by-case basis with:

  • Macrolides (azithromycin) — first-line therapy
  • Tetracyclines (tetracycline and doxycycline)
  • Fluoroquionolones

Healthcare providers shouldn't prescribe tetracyclines for young children under normal circumstances.

C. pneumoniae show in vitro resistance to the following antibiotics, which aren't recommended for treatment:

  • Penicillin
  • Ampicillin
  • Sulfa drugs

Symptoms of C. pneumoniae infection can reappear after a short or conventional course of antibiotics. Persistent infection after treatment has been demonstrated by recovery of viable bacteria; therefore, a secondary course of treatment may be recommended.

Resources

Community-acquired pneumonia (CAP) treatment guidelines

Diagnosis and Treatment of Adults with CAP
American Thoracic Society and Infectious Diseases Society of America

Management of CAP in Infants and Children Older Than 3 Months of Age
Pediatric Infectious Diseases Society and the Infectious Diseases Society of America

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Content Source:
National Center for Immunization and Respiratory Diseases; Division of Bacterial Diseases