[Emergence of hetero-VRSA strains in Japanese hospitals and its countermeasure]

Vancomycin-resistant MRSA (VRSA with MIC > or = 8 mg/L) has been described, recently. Although the incidence of VRSA has been low in Japanese MRSA strains, hetero-VRSA (heterogeneously resistant VRSA with MIC levels of 2-4 mg/L) is found in considerable abundance in Japanese hospitals, that may explain fairly frequent therapeutic failure in the vancomycin treatment of MRSA infection. Hetero-VRSA may also serve as precursor for VRSA in some clinical settings where it is exposed to high concentrations (8 mg/L or above) of vancomycin.