The rationale for revising the Clinical and Laboratory Standards Institute vancomycin minimal inhibitory concentration interpretive criteria for Staphylococcus aureus.
The Clinical and Laboratory Standards Institute (formerly, the NCCLS) established the susceptibility and resistance breakpoints for minimal inhibitory concentration (MIC) and disk diffusion testing of vancomycin against isolates of Staphylococcus aureus > 20 years ago. The disk diffusion breakpoints were modified in 1998 when it was recognized that vancomycin-intermediate S. aureus strains were not detected by this method. In 2006, the vancomycin MIC breakpoints for S. aureus were lowered (from < or = 4 microg/mL to < or = 2 microg/mL for "susceptible," from 8-16 microg/mL to 4-8 microg/mL for "intermediate," and from > or = 32 microg/mL to > or = 16 microg/mL for "resistant") to increase detection of heterogeneously resistant isolates of S. aureus. This decision reflected a growing amount of microbiological and clinical data indicating that isolates of S. aureus are less likely to respond to vancomycin therapy when the vancomycin MICs are > or = 4 microg/mL.
Tenover
Fred C
FC
Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. fnt1@cdc.gov
Moellering
Robert C
RC
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D013211:Staphylococcus aureus / Q000187:drug effects*; D014640:Vancomycin / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D014640:Vancomycin