15 frente 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)
16 How 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.