Rapid detection of Methicillin-Resistant Staphylococcus aureus MRSA in nose, groin, and axilla swabs by the BD GeneOhm MRSA achromopeptidase assay and comparison with culture

OBJECTIVE: To compare the BD GeneOhm Methicillin Resistant Staphylococcus aureus (MRSA) Achromopeptidase (ACP) polymerase chain reaction (PCR) assay with the culture method for the detection of MRSA colonization.

METHODS: One hundred and two patients were admitted to the Intensive Care Unit in King Khalid Hospital, Najran, Kingdom of Saudi Arabia from July 2010 to February 2011. Separate swabs from the nose, axilla, and groin of each patient were processed by the culture method (sheep blood agar plate and mannitol salt agar plate) and BD GeneOhm MRSA ACP assay.

RESULTS: Of the 287 samples, 62 (21.6%) were MRSA positive by the PCR assay and 26 (9%) were MRSA positive by the culture method. The PCR method showed 88.4% sensitivity and 98.6% negative predictive value. The number of MRSA-PCR positive groin specimens was nearly the same as nasal specimens. The PCR method gave positive results in 22.5% of patients by nasal specimens, 27.5% of patients by nasal and groin specimens, and 30.4% of patients by nasal, groin, and axilla specimens. The PCR method detected 30.4% of patients as MRSA positive while the culture method detected 19.6% of patients as positive for MRSA.

CONCLUSION: The BD GeneOhm MRSA ACP assay has high sensitivity and NPV and hence is a useful screening method to exclude patients who are not colonized with MRSA.