Diagnostic utility of the polymerase chain reaction for the diagnosis of Mycoplasma pneumoniae in elderly patients with community-acquired pneumonia

Mycoplasma pneumoniae is a common cause of community-acquired pneumonia (CAP) in children and young adults, but limited information about its prevalence in the elderly is available. The polymerase chain reaction (PCR) with primers targeting the cytadhesine P1 gene and the 16S rRNA gene was analyzed for detecting M. pneumoniae in throat washings of 84 patients, aged 60-96 years, with clinical diagnosis of CAP, from September 2002 through August 2004, in Santiago, Chile. PCR results were compared with serology performed by indirect immunofluorescence (IFI). Specimens from 11 of 84 patients (13.1%) were positive for M. pneumoniae by any test. The IFI test was positive in 8 (72.7%) patients and PCR in 7 (63.6%) cases. The acute phase sera allowed diagnosis of M. pneumoniae in 5 of 11 patients (45.4%), 4 of them showing an IgM response. PCR was negative in 4 patients with positive serology and 3 patients were positive only by PCR. The two PCR primers showed 100% correlation, and a similar sensitivity; no inhibitory specimens for PCR were detected. In conclusion, M. pneumoniae should be considered as a potential etiologic agent of CAP in the elderly. Its detection must be performed by a combination of PCR and serology.