Relationship between Vancomycin-Resistant Staphylococcus aureus, Vancomycin-Intermediate S. aureus, High Vancomycin MIC, and Outcome in Serious S. aureus Infections

Vancomycin has been used successfully for over 50 years for the treatment ofStaphylococcus aureus infections, particularly those involving methicillin-resistantS. aureus . It has proven remarkably reliable, but its efficacy is now being questioned with the emergence of strains ofS. aureus that display heteroresistance, intermediate resistance, and, occasionally, complete vancomycin resistance. More recently, an association has been established between poor outcome and infections with strains ofS. aureus with an elevated vancomycin MIC within the susceptible range. This minireview summarizes the definitions, mechanisms, clinical impact, and laboratory identification of reduced vancomycin susceptibility inS. aureus and discusses practical issues for the diagnostic laboratory in testing and interpreting vancomycin susceptibility forS. aureus infections.