The emergence of Staphylococcus aureus with reduced susceptibility to vancomycin in Japan.
Within the past year, infections caused by methicillin-resistant Staphylococcus aureus (MRSA) strains with reduced susceptibility to vancomycin (MIC=8 microg/mL) have been reported in both Japan and the United States. The emergence of these strains poses a potentially serious threat to public health. After 2 such strains (Mu3 and Mu50) were identified at Juntendo Hospital in 1996, a screening program to identify MRSA strains with reduced susceptibility to vancomycin was initiated. Of 970 MRSA strains tested at 195 nonuniversity hospitals throughout Japan, 13 (1.3%) were found to have subpopulations with reduced vancomycin susceptibility (heterogeneous vancomycin resistance). Among 129 MRSA strains identified at 7 university hospitals, 12 (9.3%) demonstrated heterogeneity for vancomycin resistance; 1 of these strains had a vancomycin MIC of 7 microg/mL. Although resistance in these strains is not the result of the transfer of enterococcal vancomycin resistance genes (vanA or vanB), the clonal dissemination of MRSA strains with vancomycin-resistant subpopulations is obviously undesirable. Intensified testing of MRSA strains for resistance to vancomycin and appropriate measures for the prevention of the spread of such strains are recommended.
Department of Bacteriology, Juntendo University, Tokyo, Japan.
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Hiramatsu
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D018432:Drug Resistance, Multiple; D006801:Humans; D007564:Japan; D016106:Methicillin Resistance; D008826:Microbial Sensitivity Tests; D013203:Staphylococcal Infections / Q000188:drug therapy*; D013211:Staphylococcus aureus / Q000187:drug effects*; D014640:Vancomycin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D014640:Vancomycin