S aureus

• Susceptibility Testing• Broth microdilution or disk diffusion susceptibility testing should bedone routinely on staphylococcal isolates from clinically significantinfections.• Resistance to penicillin G can be predicted by a positive test forB -lactamase; approximately 90% of S aureus produce -lactamase.• Resistance to nafcillin (and oxacillin and methicillin) occurs in about35% of S aureus and approximately 75% of S epidermidis isolates.• The gene coded for nafcillin resistance can be detectedby PCR.