Chlamydia-like bacteria in respiratory samples of community-acquired pneumonia patients.

Chlamydia-like bacteria, obligate intracellular relatives of Chlamydia trachomatis and Chlamydophila pneumoniae, are widely distributed in nature. Using a two-step nested and semi-nested PCR approach targeting the 16S rRNA gene, we found DNA of Chlamydia-like bacteria in respiratory samples from patients with community-acquired pneumonia. Of 387 cases tested, four (1.03%) tested positive if only sequences showing less than 99.9% 16S rRNA gene sequence similarity to known Chlamydiae were considered. These included for the first time Protochlamydia amoebophila, Waddlia chondrophila, and 'Candidatus Rhabdochlamydia porcellionis'-related sequences. This study extends previous findings suggesting an association of Chlamydia-like bacteria with respiratory disease, but a causal link between these microorganisms and respiratory tract infections has yet to be established.