In vitro selection of resistance to vancomycin in bloodstream isolates of Staphylococcus haemolyticus and Staphylococcus epidermidis

Eur J Clin Microbiol Infect Dis. 1991 Dec;10(12):1007-12. doi: 10.1007/BF01984921.

Abstract

The purpose of the study was to determine whether vancomycin-resistant strains of Staphylococcus haemolyticus could be selected regardless of the initial MIC of vancomycin. Twenty-one bloodstream isolates of Staphylococcus haemolyticus were studied by broth and agar selection methods. The broth method selected strains for which MICs of vancomycin ranged from 4 to 32 micrograms/ml and MBCs from 16 to greater than 128 micrograms/ml. The agar method selected strains for which MICs ranged from 8 to 32 micrograms/ml and MBCs from 8 to greater than 128 micrograms/ml. For comparison, seven strains of Staphylococcus epidermidis were evaluated by the agar selection method. Final MICs of vancomycin ranged from 8 to 16 micrograms/ml; MBCs ranged from 16 to 64 micrograms/ml. Clearly, in vitro exposure to vancomycin can select strains of Staphylococcus haemolyticus and Staphylococcus epidermidis for which MIC values are beyond the susceptible breakpoint.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacteremia / microbiology
  • Culture Media
  • Drug Resistance, Microbial
  • Humans
  • Microbial Sensitivity Tests
  • Staphylococcal Infections / microbiology
  • Staphylococcus / drug effects*
  • Staphylococcus / isolation & purification
  • Staphylococcus epidermidis / drug effects
  • Staphylococcus epidermidis / isolation & purification
  • Vancomycin / pharmacology*

Substances

  • Culture Media
  • Vancomycin