Evaluation of tube coagulase and a fluorogenic substrate for rapid detection of methicillin-resistant Staphylococcus aureus from selective enrichment broth in an outbreak of EMRSA 15.

We investigated the use of tube coagulase and a fluorescent substrate, N-t-BOC-val-pro-arg-7-amido-4-methylcoumarin for the rapid detection of MRSA in selective broth enrichment cultures during an outbreak. These methods were compared with direct plating of swabs and plating a selective broth enrichment culture using 200 screening swabs collected from forty patients during the investigation of an outbreak of E-MRSA 15. Overall 66 swabs were positive for MRSA following subculture of broth enrichment culture. Direct plating detected 25 (38%) positives, tube coagulase 37 (56%), and fluorescent substrate 49 (74%) respectively, although nine of the 49 turned out to be false reactions. When detection from individual patients was analyzed, selective broth subculture identified 28 patients colonized with MRSA. Direct plating detected only 12 (43%) of these patients. The tube coagulase and fluorescence methods detected MRSA in 17 (60%) and 19 (68%) patients respectively. The tube coagulase method was found to be 100% specific for MRSA suggesting its use as a rapid method for the detection of MRSA from selective enrichment broth.