Table 2.

β-Lactam Resistance Mechanisms in Staphylococci, Detection Methods, and Reporting Recommendations^a

Resistance Mechanism	Organism	Detection and Reporting: CLSI	Detection and Reporting: EUCAST
blaZ-mediated penicillinase (penicillin resistance)	All Staphylococcus species	Penicillin disk zone edge for S. aureus or induced β-lactamase test (Nitrocefin) for all CoNS	Penicillin disk zone edge for all Staphylococcus (notes that cephalosporin-based β-lactamase tests are unreliable for staphylococcal penicillinase)
mecA-mediated oxacillin resistance, PBP2a (oxacillin resistance)	S. aureus, S. lugdunensis	Cefoxitin disk diffusion or MIC, oxacillin MIC, mecA PCR, or PBP2a detection	Cefoxitin disk diffusion or MIC, oxacillin MIC, mecA PCR, or PBP2a detection
	CoNS	Cefoxitin disk diffusion or oxacillin MIC, mecA PCR, or PBP2a detection	Cefoxitin disk diffusion or oxacillin MIC, mecA PCR, or PBP2a detection
mecC-mediated oxacillin resistance	S. aureus, (1 report in CoNS)	Cefoxitin disk diffusion or MIC, oxacillin MIC, mecC, PCR	Cefoxitin disk diffusion or MIC, oxacillin MIC, mecC PCR

Abbreviations: CLSI, Clinical and Laboratory Standards Institute; CoNS, coagulase-negative staphylococci; EUCAST, European Committee on Antimicrobial Susceptibility Testing; MIC, minimum inhibitory concentration; PBP2a, penicillin-binding protein 2a; PCR, polymerase chain reaction.

^aCeftaroline resistance for Staphylococcus aureus can be determined by performing disk diffusion or MIC susceptibility testing.