Current status of antimicrobial susceptibility in MRSA isolates typed by coagulase and phage typing in Okinawa.

The incidence of nosocomial infections with methicillin-resistant Staphylococcus aureus is of great concern in Japan and the developed world as a whole. Simple typing techniques like coagulase and phage typing are quick and useful for monitoring and evaluating these organisms. In view of this, the current status of antimicrobial susceptibility in Staphylococcus aureus (S. aureus) isolates in Okinawa typed by coagulase and phage typing was studied. Of 508 isolates, methicillin-resistant S. aureus (MRSA) comprised 54.3% (minimum inhibitory concentration (MIC) > or = 16 micrograms/ml). Coagulase type II and phage group III were the most prevalent, comprising 65.2% and 38%, respectively. These were followed by phage non-typable group and coagulase type III with 36.6% and 12.7%, respectively. Compared to a previous study conducted in 1989, there has been an increase of about 17% in the MRSA isolation rate with a concomitant increase of about 11% in the coagulase type II MRSA isolation rate and a decrease of about 27% in the isolation rate of coagulase type III MRSA. Using a panel of 16 antibiotics, coagulase type II MRSA were resistant to all except Arbekacin and Vancomycin. Arbekacin and Vancomycin were the sole antibiotics to which resistance was not expressed by any of the isolates. With regard to the methicillin-sensitive S. aureus (MSSA), coagulase type III and phase group III were the most prevalent, comprising 25.9% and 32.3%, respectively.