A study was conducted over a 4-month winter period within a family practice in Madison WI to identify whether C. pneumoniae (Cpn) and M. pneumoniae (Mpn) are common etiological agents of respiratory tract infections (RTI).

Twenty patients diagnosed by clinical criteria to have either acute or chronic RTI and 27 healthy control subjects were tested in this study. Nasopharyngeal swab specimens and sera were obtained from both subject populations and oral washes were obtained only from those patients diagnosed with RTI. DNA extracted from nasopharyngeal swab specimens and oral washes were analyzed with species-specific quantitative real-time PCR (qPCR) assays that previously were validated with both dosed and patient positive nasopharyngeal swabs. The qPCR results were then compared to serological data acquired with commercially available Mpn and Cpn IgM kits.

All respiratory samples analyzed with qPCR assays were negative for Cpn and Mpn DNA. The prevalence of Cpn- and Mpn-specific IgM antibodies was found to be 1/20 (5%) and 5/20 (25%) for patients diagnosed with RTI and 2/27 (7%) and 1/27 (4%) for healthy control subjects.

Analysis of the non-invasively obtained respiratory samples with qPCR indicates that active infection with Cpn and Mpn are infrequent within the patient population investigated here. The serological evidence does indicate that the prevalence of Mpn infection may be higher in the clinical cases than in controls. In light of this data, other sampling methods might be necessary for the routine detection of Cpn and Mpn by qPCR especially in cases where antibiotic therapy has been initiated.