[Isolation and antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) at Kumamoto University Hospital].

An increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) has created a serious therapeutic problem. During the period from July to December 1987, the prevalence of MRSA was only 72 strains (35.8%) of 201 total staphylococcal isolates. Since then, the frequency of MRSA has markedly increased to 67.3% in 1989, and at that time it was estimated that 30 patients (3.5%) of 850 total inpatients became infected with MRSA. In an early study in 1987, the majority of the MRSA came from post-operative patients; however in 1989, nearly 40% of MRSA were from internal medicine, mainly from immunocompromised patients. The major source of MRSA isolates was sputum (40%) throughout the years, but the MRSA from blood cultures was first recovered in 1989. Also, the major coagulase serotype of MRSA was type IV (18 of 30) in the 1987-study, then shifted to type II (24 of 40) in 1989. Among the several antimicrobials evaluated, four agents; erythromycin, minocycline, ofloxacin, and gentamicin revealed increasing MICs when compared with the results obtained for the MRSA isolates in 1987 and 1989. In particular, the most of the MICs to minocycline and ofloxacin were categorized to be highly susceptible (less than or equal to 0.39 micrograms/ml) or resistant (greater than or equal to 25 micrograms/ml). Vancomycin, currently licensed for the MRSA infection, will be highly effective both in vitro and in vivo; however, it examinative of the MRSA isolates in the clinical laboratories, especially to prevent hospital-acquired infections and to follow up the vancomycin susceptibility will be required.