Gene mecA provides Staphylococcus aureus resistance to which antibiotics?

The gene mecA is critical for conferring resistance in Staphylococcus aureus to certain beta-lactam antibiotics, namely methicillin, oxacillin, and penicillin. This gene encodes for a modified penicillin-binding protein (PBP), PBP2a, which has a much lower affinity for beta-lactam antibiotics compared to the usual PBPs found in susceptible strains. Consequently, the presence of mecA enables Staphylococcus aureus to survive in the presence of these antibiotics, making infections difficult to treat with standard penicillin-type medications.

In contrast, the other choices include antibiotics that mecA does not provide resistance against. For example, vancomycin, while commonly used to treat various Staphylococcus aureus infections, is not affected by mecA and is often used as a last-resort treatment for methicillin-resistant strains. Gentamicin and tetracycline, listed in another choice, are aminoglycoside and tetracycline antibiotics, respectively, and are not related to the mecA mechanism. Finally, rifampin and erythromycin also do not relate to the action of mecA, as they target different bacterial functions and pathways. Thus, the identification of methicillin, oxacillin,