15frente a Staphylococcus coagulasa negativos (CoNS) MICsOxacillin SusceptibleOxacillin IntermediateOxacillin ResistantS. aureus<2 g/mlno intermediate MIC>4 g/mlCoNS<0.25 g/ml>0.5 g/mlZone sizes>13 mm11-12 mm<10 mm>18 mmno intermediate zone<17 mmPuntos de corte (breakpoints) de MIC y disco-difusión para oxacilina frente a S. aureus yfrente a Staphylococcus coagulasa negativos (CoNS)
16How is the mecA gene involved in the mechanism of resistance How is the mecA gene involved in the mechanism of resistance? Staphylococcal resistance to oxacillin/methicillin occurs when an isolate carries an altered penicillin-binding protein, PBP2a, which is encoded by the mecA gene. The alteration of the penicillin-binding protein does not allow the drug to bind well to the bacterial cell, causing resistance to -lactam antimicrobial agents.