What media and technique is suggested for detecting mecA mediated resistance in MRSA?

The detection of mecA mediated resistance in Methicillin-resistant Staphylococcus aureus (MRSA) is best accomplished using Mueller-Hinton agar with a cefoxitin disk incubated at 35°C. This method is favored because cefoxitin is a cephalosporin antibiotic that provides a more accurate assessment of methicillin resistance in staphylococci due to its structural similarity to methicillin itself.

When MRSA strains possess the mecA gene, which encodes for an altered penicillin-binding protein (PBP2a), they exhibit resistance to cefoxitin. The use of cefoxitin in disk diffusion tests helps in determining the susceptibility or resistance of the bacteria to beta-lactam antibiotics, making it a reliable indicator of methicillin resistance. Incubation at 35°C is optimized for the growth of Staphylococcus aureus, ensuring clear results in the interpretation of the sensitivity pattern.

Other media and techniques listed may not effectively characterize the mecA-mediated resistance or are not standard for testing MRSA. For example, blood agar with streptomycin and MacConkey agar with gentamicin are not typically used for this specific resistance detection, while chocolate agar with vancomycin is not relevant for assessing ce