Serological and molecular detection of Mycoplasma pneumoniae in patients with community-acquired pneumonia

Background and objectives Mycoplasma pneumoniae is an important but underdiagnosed cause of community-acquired pneumonia (CAP). This study evaluated the utility of combined serological and molecular testing for detection of M. pneumoniae among adult and paediatric CAP patients from Kashmir, North India, and characterised circulating strains. Methods In this prospective hospital-based study, 260 patients with CAP were investigated. Respiratory specimens were tested by PCR targeting the P1 adhesin gene, and serum samples were analysed for M. pneumoniae -specific IgM and IgG antibodies using ELISA. Selected PCR-positive samples were subjected to Sanger sequencing. Results Overall, 27.3% (71/260) of patients were positive by combined molecular and serological testing. Positivity rates were higher among adults compared to paediatric patients [31.9% (58/182) vs . 16.7% (13/78)]. Seropositivity was observed in 25.8% (67/260) of cases, while PCR detected M. pneumoniae in 9.2% (24/260). Using PCR as the reference standard, ELISA demonstrated 83.3% sensitivity and 80.1% specificity. Conversely, with ELISA as the reference, PCR showed high specificity (97.9%) but low sensitivity (29.8%). The combined molecular–serological approach yielded the highest diagnostic accuracy [(area under the curve (AUC)=0.852], outperforming PCR alone (AUC=0.669) and IgM ELISA alone (AUC=0.803). Sequencing of representative isolates revealed ≥99% nucleotide identity with globally circulating type M. pneumoniae strains. Interpretation and conclusions M. pneumoniae contributes substantially to CAP in this setting. A combined molecular-serological approach improves diagnostic yield.