Comparison of light cycler PCR and conventional susceptibility testing for detection of MRSA from cultures

OBJECTIVE: To compare a duplex light cycler polymerase chain reaction (PCR) assay targeting the mecA gene and a Staphylococcus aureus (S. aureus) specific marker and the conventional method.

METHODS: We evaluated 400 samples sent to the laboratory in Zayed Military Hospital, Abu Dhabi, United Arab Emirates for methicillin-resistant Staphylococcus aureus (MRSA) screening and routine bacterial cultures from the period January 2003 to January 2004. All samples were cultured and identified according to the National Committee for Clinical Laboratory Standard guidelines. Staphylococcus aureus were tested for methicillin susceptibility according to the guidelines. All Staphylococcus positive cultures underwent testing by the new duplex light cycler PCR assay. We used 2 pairs of primers: mecA and nuc. Both targeted the mecA gene and the S. aureus-specific marker. Results obtained from the 2 methods (conventional culture method and the real-time PCR method) were compared.

RESULTS: From the 400 samples tested, a total of 9 MRSA were detected by both methods. The real-time PCR method took less than 60 minutes to complete.

CONCLUSION: This study shows that the duplex light cycler PCR assay method is very sensitive, very specific, and less time consuming in diagnosing MRSA from bacterial cultures.