Investigation of beta-lactam antibiotic-induced vancomycin-resistant MRSA (BIVR).

We could not detect hetero-vancomycin-intermediate resistant Staphylococcus aureus (hetero-VISA), according to the definition of hetero-VISA, from the clinical isolates of 140 methicillin-resistant S. aureus (MRSA) strains. However, 15 beta-lactam antibiotic-induced vancomycin-resistant MRSA (BIVR) strains were detected from the same strains. We screened 1882 MRSA clinical isolates obtained in 2002 from 21 institutes throughout Japan. The detection rate of blood-isolated BIVR was 12.6% (19/151), and that of nonblood-isolated BIVR was 4.9% (85/1731; P < 0.001; chi2 test). Uridine-diphosphate-N-acetylmuramyl-L: -alanyl-D: -isoglutamyl-L: -lysine, used as the peptidoglycan material of S. aureus, showed the same results as beta-lactam antibiotics in BIVR.