Mycoplasma contamination of chlamydiae isolated from clinical specimens.

Ten Chlamydia pneumoniae strains were screened for Mycoplasma contamination using two differently designed Mycoplasma-specific polymerase chain reactions (PCR). The primers of the Mycoplasma-specific PCR designed by Spaepen et al. (9) cross-reacted with all of the C. pneumoniae strains giving false-positive results. When the 10 strains of C. pneumoniae were tested for mycoplasmas with the PCR designed by Harasawa et al. (5), only 3 were positive. Mycoplasmas were cultured from these three C. pneumoniae strains confirming the latter PCR results. The PCR of Harasawa et al. (5) was highly specific for mycoplasmas and did not cross-react with C. pneumoniae. These findings suggest that chlamydiae should be periodically screened for Mycoplasma contamination. Careful attention to primer design is important if PCR is chosen as the screening method.