Comparison of PCR and culture tests for diagnosis of Mycoplasma pneumoniae respiratory tract infections

Backgrounds & Mycoplasmas pneumoniae is responsible for more than 20% of community acquired pneumonia cases and also implicated in acute respiratory infections, such as sore throat, pharyngitis, rhinitis, and tracheobronchitis. Conventional assays for the detection of M. pneumoniae have their limitations, resulting in the need for more accurate diagnostic methods. Molecular methods, for example Polymerase Chain Reaction (PCR), have the potential to produce rapid, sensitive, and specific results, allowing early appropriate antibiotic therapy. In this study, we aimed to compare PCR and culture results and to develop a rapid and more practical PCR technique for detection of M. pneumoniae. Clinical samples from 100 patients with respiratory complaints were subjected to culture and PCR. A highly sensitive, PCR protocol using P4A and P4B primers targeting the P1 cytadhesin gene was designed and applied to nasopharyngeal swab samples collected from patients. Amplicon (345 bp) cloned by PCR-cloning and then sequenced by dideoxy chain termination. The results of positive cultures (10 out of 100) well correlated with the results of PCR. Samples from 33 additional patients which showed a negative result in culture, were positive by PCR. The detection limit for this assay was found to be 10 M. pneumoniae organisms in clinical samples. There was no amplification of DNA from 11 other species of human and animal mycoplasmas and 17 other bacterial species. This study indicates that PCR is a sensitive, specific and reliable method for rapid diagnosis of M pneumoniae in respiratory tract samples.