[Clinical manifestations of Chlamydia pneumoniae infections]

Chlamydia pneumoniae is a newly described and ubiquitous bacterium. Most infections are asymptomatic as shown by a high worldwide seroprevalence (> 50% of cases). It is a common cause of acute respiratory infections, mainly pneumonia (> 50% of cases) and other acute respiratory tract infections (25% of acute bronchitis, < 5% of sinusitis, otitis and pharyngitis). About 10% of the community acquired pneumonia cases have been associated with Chlamydia pneumoniae infection. This incidence depends on a cyclic epidemiology with a high incidence for 2 to 3 years followed by a low prevalence for 3 to 4 years. Most chlamydial infections are mild but occasionally severe with death especially in old people. Mostly acute infections are recurrent infections. The seroprevalence is higher in asthmatic patients, its role in acute exacerbation of chronic bronchitis is not definitely established. Extra-respiratory acute infections are less frequent, either fever alone, or cardiovascular diseases (acute myocarditis, pericarditis and endocarditis) or neurological (encephalitis, meningitis or Guillain-Barré syndrome). In addition, seroepidemiology studies have shown an association with coronary artery disease, Chlamydia pneumoniae was detected in coronary atheroma by immunochemistry, polymerase chain reaction and by electron microscopy. Chlamydia pneumoniae may be involved in the atherosclerotic process. To define the clinical spectrum of infection requires precise laboratory diagnosis, the most efficient tests (PCR, direct immunofluorescence and culture) are done in specialized laboratories, serological tests are less reliable. Macrolides, cyclines and fluoroquinolones are the most potent antibiotics but with differences in vitro within and between these families of antibiotics. Bacteriological failures are described despite the in vitro activity. A lot of questions on clinical aspects, epidemiology and treatment are unanswered, we need more studies.