Multiplex PCR-ELISA for direct detection of MRSA in nasal swabs advantageous for rapid identification of non-MRSA carriers

In the study presented here 251 nasal swabs obtained from medical staff were directly investigated for MRSA using a commercial multiplex PCR system in parallel with conventional culture methods to determine the usefulness of PCR for rapid screening. Both methods identified 3.2% (8/251) of specimens as MRSA-positive; one sample was culture-positive only, and three were PCR-positive only. PCR correctly identified 215 of 239 (90%) negative swab samples, but one sample with weak cultural growth was not detected and was therefore considered false negative. The comparative sensitivity of culture versus PCR was 75% (9/12) versus 91.6% (11/12). Although PCR had a low positive predictive value (31.4%) its negative predictive value was high (99.5%). The results of this study indicate the multiplex PCR is suitable for the rapid identification of MRSA-negative individuals directly from nasal swabs in populations with a low MRSA prevalence, but positive results need to be confirmed by culture.