Chlamydophila pneumoniaewas rarely detected in bronchoalveolar lavage fluid in patients with bacterial pneumonia using molecular methods

Background and Objectives: Chlamydophila pneumoniae has been recognized as one of common causes in pneumonia and acute respiratory tract infection. Serological analysis is commonly used but it is not enough accurate and convenient for diagnosing C. pneumoniae pneumonia in the real-world clinical setting. Therefore, the true prevalence of C. pneumoniae pneumonia seems to be unclear. In addition, no C. pneumoniae were detected in 16S rRNA gene analysis in our previous study. The aim of this study was to detect C. pneumoniae using two specific PCR methods using bronchoalveolar lavage fluid (BALF) samples in patients with pneumonia. Methods: BALF samples from 147 patients with bacterial pneumonia were retrospectively evaluated using two C. pneumoniae -specific PCR method. Results: None of them was positive for specific PCR for C. pneumoniae using two sets of specific primers and 16S rRNA gene analysis. On the contrary, serological analysis revealed that 1 of 38 (2.6%) patients was presumptive as acute infection of C. pneumonia e and 15 of the 94 (16.0%) patients were considered as doubt of acute C. pneumoniae . Cultivation and/or 16S rRNA gene sequencing revealed that streptococci, H. influenzae , and M. pneumoniae were detected in presumptive/doubted cases according to serological method. Conclusions: No C. pneumoniae DNA was detected in BALF samples from patients with pneumonia, even though molecular modalities were applied. These results may suggest that C. pneumoniae may be extremely few in the lower respiratory tract in patients with pneumonia, and physicians may consider low possibility of C. pneumoniae as causative pathogen.