CHARACTERIZATION OF STAPHYLOCOCCUS-AUREUS ISOLATES WITH DECREASED SUSCEPTIBILITY TO VANCOMYCIN AND TEICOPLANIN - ISOLATION AND PURIFICATION OF A CONSTITUTIVELY PRODUCED PROTEIN ASSOCIATED WITH DECREASED SUSCEPTIBILITY

Derivative isolates with 4- to 8-fold and 8- to 16-fold increases in MICs of vancomycin and teicoplanin, respectively, were selected from 2 susceptible dinical isolates of Staphylococcus aureus by serial incubation in low-level vancomycin. A protein of approximately 39 kDa was demonstrable in the cytoplasmic fraction and occasionally in the membrane fraction by SDS-PAGE of both derivatives. This protein was purified by DEAE chromatography, preparative SDS-PAGE, and electroelution. Derivative bacteria were larger on transmission electron microscopy, had thicker cell wags, and had changes in colony morphology on solid media. Further evidence for cell wall reorganization included loss of phage and capsular typing, decreased susceptibility to lysostaphin/lysozyme lysozyme killing, and changes in condition for detection of optimal coagulase activity. The mechanism of decreased susceptibility to glycopeptide antibiotics among S. aureus derivative isolates is uncertain. The production of the approximately 39-kDa cytoplasmic protein and cell wall reorganization may mediate changed affinity of glycopeptide-peptidoglycan binding or impairment of glycopeptide access to its cell wall target.