Serological and molecular methods in diagnosis of lower respiratory tract infections caused due to Chlamydia pneumoniae

Abstract

Introduction: Lower respiratory tract infections (LRTIs) continue to be a major health problem in children. Increasingly “atypical” agents such as Chlamydophila pneumoniae are being recognized as a significant cause of LRTI. The current study evaluated serological and molecular methods in detection of LRTI due to C. pneumoniae in young children. Materials and Methods: Serum and nasopharyngeal aspirate (NPA) were collected from 53 treatment-naïve children (6 months–6 years) with LRTI. Immunoglobulin M (IgM) and IgG antibodies to C. pneumoniae were detected in serum by enzyme-linked immunosorbent assay (ELISA) and microimmunofluorescence (MIF) test. Nonnested polymerase chain reaction (PCR) to detect a 183-bp fragment of the 60-kDa outer membrane protein 2 of C. pneumoniae was performed on DNA extracted from the NPA samples. Results: Of the 53 children tested, 14 (26.4%) children were diagnosed to have acute C. pneumoniae infection according to CDC guidelines. When compared with IgM MIF (reference test), PCR and IgM ELISA showed a sensitivity of 36% and 71%, respectively, and a specificity of 100%. IgG antibodies were positive in an additional 8 cases, by both MIF and ELISA, suggesting “possible” reinfection. Conclusion: This study despite its drawbacks provides evidence that C. pneumoniae is a significant cause of LRTI in young children.