Characterization of MRSA transmission in an emergency medical center by sequence analysis of the 3′-end region of the coagulase gene

The distribution of methicillin-resistant Staphylococcus aureus (MRSA) isolates at the St. Marianna University affiliated emergency medical center (EMC) was studied by sequence analysis of the 3′-end region of the coagulase gene. We collected a total of 42 MRSA isolates, consisting of 20 strains from the hospital environment, 13 strains from the nostrils or fingers of medical staff, and 9 strains from inpatients in the EMC. We compared our results with those from 27 stock strains of known coagulase serotype and 2 strains reported in the literature. All 69 strains tested have four to six tandem repeats in the 3′-end region of the coagulase gene. Among the 42 MRSA isolates collected, the base sequence of the 3′-end region of the coagulase gene was identical in 28 of them (67%). The number of isolates originating from the hospital environment, medical staff, and patients, respectively, that were identical to this representative strain were 18 (90%), 6 (46%), and 4 (44%). Phylogenetic analysis using the DNA sequences of the tandem repeat region demonstrated that almost all strains from the patients formed a concordant cluster with the representative strain from the hospital ward. We also assessed the value of sequence analysis of the 3′-end region of the coagulase gene as an epidemiological marker. Our results indicate that sequence analysis of the 3′-end region of the coagulase gene of MRSA may be a potent epidemiologic typing system.