A patient diagnosed with a methicillin-resistant Staphylococcus aureus infection may be treated with which medication?

The appropriate treatment for a methicillin-resistant Staphylococcus aureus (MRSA) infection is daptomycin. Daptomycin is a lipopeptide antibiotic that is specifically indicated for infections caused by gram-positive organisms, including MRSA. It works by disrupting bacterial cell membrane potential, leading to cell death. Daptomycin's unique mechanism makes it effective against resistant strains of Staphylococcus aureus, which are not susceptible to traditional beta-lactam antibiotics, such as methicillin.

In contrast, metronidazole is primarily effective against anaerobic bacteria and protozoa, and does not target Staphylococcus aureus. Amoxicillin is a penicillin antibiotic that is ineffective against MRSA, as it is designed for susceptible strains of Staphylococcus. Fidaxomicin is used to treat Clostridium difficile infections and not for treating Staphylococcus infections. Therefore, daptomycin is the best choice for treating a patient with a diagnosed MRSA infection.