CLINICAL ASPECTS OF CHLAMYDIA-PNEUMONIAE INFECTION

This recently recognised member of the genus Chlamydia is one of the m ost widespread pathogens of man, though up to 90% of infected people h ave few or no symptoms. Several studies have estimated the population prevalence of antibodies to C. pneumoniae at 40-55% in the northern he misphere, and over 60% in under-developed countries. The incidence of infections follows a cyclical pattern, with peaks at regular intervals of 2-10 years, but no apparent seasonal periodicity. Nosocomial trans mission may be mediated by environmental surfaces as well as aerosols, and immunosuppression, for example by the human immunodeficiency viru s, predisposes to infection. Chlamydia pneumoniae causes predominantly atypical pneumonia, often severe in adults, especially the elderly; i ncluding 5-10% of community-acquired pneumonia in Scandinavian countri es. Serological evidence indicates associations with asthma, bronchiti s, exacerbations of chronic airflow obstruction, otitis media and bron chiolitis. Several studies, using both serological and morbid anatomic al techniques, also indicate associations with vascular atheroma and i schaemic heart disease, and with acute myocardial infarction. Chronic, latent and recurrent infections have been documented, and it is postu lated that, like chronic or recurrent C. trachomatis infections, these may produce disease as a consequence of the host's immunological hype rsensitivity. Several techniques are available for serological diagnos is: the technique of choice is microimmunofluorescence, using fixed wh ole elementary or reticulate bodies as antigen, but antibody responses are highly variable. Traditional alternatives, antigen detection (by direct immunofluorescence or enzyme immunoassay) and cell culture, hav e major disadvantages. Polymerase chain reactions have not yet been wi dely applied to the clinical setting. Tetracycline antibiotics, erythr omycin and quinolones are not very efficacious in the treatment of C. pneumoniae infection. The azalide antibiotic, azithromycin, and the ma crolide, clarithromycin, are active in vitro against C. pneumoniae, an d may become treatments of choice. The development of anti-chlamydial vaccines remains an important research goal.