Due to the ongoing concern about the reliability of Staphylococcus breakpoints (interpretive criteria) for other β-lactam agents, the Clinical and Laboratory Standards Institute recently approved the elimination of all breakpoints for antistaphylococcal β-lactams except for penicillin, oxacillin or cefoxitin, and ceftaroline. Routine testing of penicillin and oxacillin or cefoxitin should be used to infer susceptibility for all β-lactams with approved clinical indications for staphylococcal infections. It is critical for laboratories to reject requests for susceptibility testing of other β-lactams against staphylococci and to indicate that susceptibility to these agents can be predicted from the penicillin and oxacillin or cefoxitin results. This article reviews β-lactam resistance mechanisms in staphylococci, current antimicrobial susceptibility testing and reporting recommendations for β-lactams and staphylococci, and microbiologic data and clinical data supporting the elimination of staphylococcal breakpoints for other β-lactam agents.
Keywords: CLSI breakpoints; Staphylococcus susceptibility; β-lactams and Staphylococcus.