Evaluation of tube coagulase and a fluorogenic substrate for rapid detection of methicillin-resistant Staphylococcus aureus from selective enrichmentbroth 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 enrich ment culture using 200 screening sn abs collected from forty patients durin g the investigation of an outbreak of E-MRSA 15. Overall 66 swabs were posi tive for MRSA following subculture of broth enrichment culture. Direct plat ing detected 25 (38%) positives, tube coagulase 37 (56%), and fluorescent s ubstrate 49 (74%) respectively, although nine of the 49 turned out to be fa lse reactions. When detection from individual patients was analyzed, select ive broth subculture identified 28 patients colonized with MRSA. Direct pla ting detected only 12 (43%) of these patients. The tube coagulase and fluor escence methods detected MRSA in 17 (60%) and 19 (68%) patients respectivel y. The tube coagulase method was found to be 100% specific for MRSA suggest ing its use as a rapid method for the detection of MRSA from selective enri chment broth.