Relevance of Chlamydia pneumoniae in community-acquired respiratory infections.

Genus Chlamydiae is composed of smuJI bacteria, presenting unique c haracteristics such as intracellular habitat and a specitic replication cycle different from conventional bacterin. There are different species of Chlamydiae that can infect animals and men. The best known are Chlamydia traclwmaris and Chlamydia psiiiCici. TW AR is a recently described bacterium of lhe genus Ch lamydia. which was originally isolated in 1965 from the <:.onjunctiva of a Taiwanese child. The organism was first assumed to be C/Jiamydia trachomatis, until its growth in cell culture suggested it to be Chlamydia psittaci [1]. However, on the basis of ultrastructure studies and deoxyribonuc leic acid (DNA) ho mology, a new Chlamydia species named Chlamydia pnewnoniae has been identified [2]. Until now, only two strains or serovars, the TWAR and the lOL-207 strain, have been found [2, 3]. The most well studied is Chlamydia TW AR. This microorganism, unlike Chlmnydia trachomaris. cannot be :.exually-transmi.lled nor be n cause of conjunctivitis [4 j. Since Chlamydia pneumoniae strain TW AR was llrsr reported to be the respiratory pathogen causing an unusual epidentic in norll1em Finland l5J, several publications ha ve confirmed the high prevalence (up to 60%) of antibodies to this organism in adults [6], and also its importance as a "new" respiratory pathogen in the spectrum of community-acquired pulmonary infections. GRAYSTON and eo-workers [1) were the first to point out the importance of Chlamydia pneumoniae strain TW AR as a respiratory pathogen. They demonstrated that it accounted for 12% of 76 episodes of pneumonia. 5% of bronchitis, and I% of pharyngitis, in a population of university students. Studying hospital ized patients wirh community-acquired pneumonia in Nova Scotia, a 6% prevalence of this infection was found [7 1. More recent reports [8. 9j investigating both the epidemiology and the aetiology of community-acquired pneumonia in patients requiring hospitalization. have shown that this "new" pathogen is a frequent cause of pneumonia, and may even be responsible for one third of the cases of pneumonia [9]. In older populations, the role of Chlamydia pneumoniae strain TW AR in community-acquired pneumonia has been also shown [lO]. In the present issue of this