A 45-year-old man is hospitalized for the treatment of severe cellulitis of the right lower extremity. On admission, blood cultures were drawn, and he was started on empiric intravenous vancomycin and ceftriaxone. On hospital day 3, the patient is afebrile, and the erythema has significantly decreased. The blood cultures return positive for Staphylococcus aureus. Susceptibility testing shows the organism is resistant to penicillin but susceptible to oxacillin, cefazolin, and vancomycin. Which of the following is the most appropriate next step in antibiotic therapy?
- AContinue both intravenous vancomycin and ceftriaxone
- BDiscontinue current antibiotics and start intravenous ceftriaxone
- Discontinue current antibiotics and start intravenous cefazolinAnswer
- DContinue intravenous vancomycin and discontinue ceftriaxone
- EDiscontinue current antibiotics and start intravenous piperacillin-tazobactam
Answer
Discontinue current antibiotics and start intravenous cefazolin
The patient has bacteremia caused by methicillin-susceptible Staphylococcus aureus (MSSA), confirmed by its susceptibility to oxacillin. For MSSA bacteremia, targeted therapy with a beta-lactam antibiotic, such as a first-generation cephalosporin (e.g., cefazolin) or an anti-staphylococcal penicillin (e.g., nafcillin, oxacillin), is the standard of care. These agents exhibit rapid bactericidal activity and have been proven superior to vancomycin for MSSA, leading to lower mortality rates, reduced risk of relapse, and faster clearance of bacteremia. Therefore, the empiric regimen should be discontinued, and the patient should be switched to intravenous cefazolin.
Step-by-Step Solution
Key Concept
The treatment of choice for methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia is an intravenous anti-staphylococcal penicillin (e.g., nafcillin, oxacillin) or a first-generation cephalosporin (e.g., cefazolin), which provide superior outcomes compared to vancomycin.
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