American Board of Internal Medicine (ABIM) Certification Practice Exam

For patients unable to take vancomycin, which antibiotic is an effective alternative for treating methicillin-resistant Staphylococcus aureus?

1. Daptomycin

2. Linezolid

3. Clindamycin

4. Tigecycline

The correct answer is: Daptomycin

Daptomycin is an effective alternative for treating methicillin-resistant Staphylococcus aureus (MRSA) in patients who are unable to take vancomycin. This antibiotic belongs to the lipopeptide class and works by disrupting bacterial cell membrane potential, leading to cell death. It is particularly useful in serious MRSA infections, including those associated with bacteremia and skin and soft tissue infections. Daptomycin has favorable pharmacokinetics and demonstrates good efficacy against MRSA, making it a suitable choice when vancomycin cannot be used, whether due to allergy, renal impairment, or treatment failure. Additionally, it has a unique mechanism of action that allows it to remain effective against strains of MRSA that may be resistant to beta-lactams and other agents. In contrast, while linezolid, clindamycin, and tigecycline are also used to treat MRSA, each has particular clinical scenarios where they are preferred over daptomycin depending on the type and severity of infection, renal function, and concerns about potential side effects. For instance, linezolid is effective for pneumonia and soft tissue infections, clindamycin offers good coverage for certain skin infections, and tigecycline,