Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a major nasocomial pathogen. The active surveillance of MRSA is essential to limit its transmission. The BD GeneOhm MRSA real-time PCR assay (Becton Dickinson Diagnostics, San Diego, USA) has been recently developed and used for same-day MRSA detection directly from nasal swab specimens. The authors of the present study compared GeneOhm MRSA PCR with culture methods to evaluate its diagnostic performance for MRSA active surveillance. 

Methods: The present study was conducted on patients admitted to the ICU for six months. A total of 371 nasal swab specimens were obtained from patients at admission day and at the seven-day follow-up. The swab was streaked onto culture media, and presumptive S. aureus colonies were confirmed as MRSA using the BD Phoenix automated microbiology system (Becton Dickinson Diagnostic Systems, Sparks, USA). In addition, GeneOhm MRSA PCR was performed. For discrepant results between GeneOhm MRSA PCR and culture, the enrichment broth culture method was performed. 

Results: There were 34 samples with discrepant results between the GeneOhm MRSA PCR and culture. The overall agreement was 90.7%. For the detection of MRSA, the GeneOhm MRSA PCR was 96.8% sensitive and 86.3% specific, with positive and negative predictive values of 83.9% and 97.3%, respectively. 

Conclusion: Identification of MRSA-colonized patients was achieved in as little as two hours, and the high negative predictive value of GeneOhm MRSA PCR suggests that the assay is a rapid method for the identification of persons who are not colonized with MRSA. However, due to the low positive predictive value, GeneOhm MRSA PCR combined with enrichment culture in cases of positive GeneOhm MRSA PCR is potentially useful for active MRSA surveillance activities. (Korean J Clin Microbiol 2011;14: 74-78)