Interactions between methicillin and vancomycin in methicillin-resistant Staphylococcus aureus strains displaying different phenotypes of vancomycin susceptibility

Valacomycin-sensitive, -intermediate, and -heterointermediate methicillin-r esistant Staphylococcus ara eus isolates mere tested by using E-tests to ex plore the interaction of methicillin and vancomycin. For the vancomycin;int ermediate and -heterointermediate strains both drugs showed antagonism at c oncentrations below their MICs but synergy at methicillin concentrations ne at the MIG. This property could be used to screen for heterointermediate S. aureus strains.