Early diagnosis of community-acquired pneumonia caused by Mycoplasma pneumoniae

Background and objective: The definitive diagnosis of M. pneumoniae is encumbered by the lack of a rapid and cost-effective test of detection. The study aimed to determine if a single serological test within the first days of hospital admission may be relevant for the diagnosis of community-acquired pneumonia (CAP) caused by M. pneumoniae. Patients and methods: Patients with suspected of CAP were investigated for microbiological diagnosis based on respiratory samples (bronchoalveolar lavage, bronchial aspirate, sputum, throat rinse), blood culture and serology for detection of atypical organisms and viruses. Patients with M. pneumoniae antibody titers >= 1:160 were further investigated by polymerase chain reaction (PCR) for detection of M. pneumoniae in respiratory samples. The group of CAP by M. pneumoniae (MP-CAP) included patients with serum titers > 1: 160 of M. pneumoniae antibodies (based on a single antibody determination at admission). The control group (non-MP-CAP group) included patients with CAP by pathogens other than M. pneumoniae or with no definitive bacteriological diagnostic. Results: Twenty adults with MP-CAP and 20 controls with non-MP-CAP were included. PCR was positive in 18/20 (90%) of the MP-CAP group and negative in the 9/9 (100%) investigated patients of the non-MP-CAP group. The duration of symptoms prior to hospital admission was rather long in both groups (mean 13,2 days in the MP-CAP group and 12,7 days in the non-MP-CAP group). The MP-CAP group was significantly younger (p=0.002), had subsequently less associated comorbidities (p < 0.001) and less purulent sputum (p=0.003) than the non-MP-CAP group. Conclusion: Single serology at admission with M. pneumoniae antibody titers > 1:160 may be useful for the diagnosis of CAP caused by M. pneumoniae in hospitalized patients with a long duration of symptoms (> 12 days).