Methicillin resistance in Staphyloccous aureus is due to:Select one alternative:efflux pumpbeta-lactamase enzymealtered metabolic pathwaymecA gene

To address the question regarding methicillin resistance in Staphylococcus aureus, let's analyze the alternatives provided:

1. Efflux pump: While certain bacteria use efflux pumps to expel drugs, this mechanism is not a primary cause of methicillin resistance in S. aureus.

2. Beta-lactamase enzyme: Beta-lactam antibiotics can be broken down by beta-lactamases, but methicillin is designed to resist degradation by these enzymes. Hence, this is not the primary mechanism responsible for methicillin resistance.

3. Altered metabolic pathway: Changes in metabolic pathways can contribute to drug resistance but are not specifically responsible for methicillin resistance in S. aureus.

4. mecA gene: This gene encodes a penicillin-binding protein (PBP) that has a lower affinity for beta-lactam antibiotics, including methicillin. The presence of the mecA gene is the definitive factor for methicillin resistance in Staphylococcus aureus.

Final Answer

The correct alternative is the mecA gene.