Epidemiology

C. pneumoniae is a common cause of human respiratory diseases, primarily in young adults.

• Seroprevalence rates of 40-70% demonstrate that C. pneumoniae is widespread worldwide. Seropositivity is first detected at school age and then increases by ∼10% per decade.
• The role of C. pneumoniae in atherosclerotic disease has long been discussed, but large-scale treatment studies have cast doubts on the etiologic role of this organism in this disease.

Clinical Manifestations

The clinical spectrum of C. pneumoniae infection includes acute pharyngitis, sinusitis, bronchitis, and pneumonia.

• Pneumonia due to C. pneumoniae resembles that due to M. pneumoniae. Pts have antecedent upper-respiratory symptoms, fever, nonproductive cough, minimal findings on auscultation, small segmental infiltrates on CXR, and no leukocytosis.
  • Primary infection is more severe than reinfection.
  • Elderly pts can have severe disease.

Diagnosis

Serology is the most clinically useful means for diagnosing C. pneumoniae infection.

• The diagnosis of acute C. pneumoniae infection requires demonstration of a fourfold rise in titer between acute- and convalescent-phase serum samples.
• Culture of the organism is difficult and is not routinely attempted. PCR assays for C. pneumoniae are currently available only for research purposes.