From the Guidelines
Cefazolin is the preferred treatment for persistent Methicillin-Sensitive Staphylococcus aureus (MSSA) bacteremia, with some studies suggesting its superiority over other antistaphylococcal penicillins like nafcillin 1.
Key Considerations
- Ertapenem is not typically used for MSSA bacteremia, as it is a carbapenem with a broader spectrum of activity than necessary for MSSA 1.
- Cefazolin has a preferable safety profile compared to antistaphylococcal penicillins like nafcillin, making it a popular choice for MSSA bacteremia 1.
- The cefazolin inoculum effect (CzIE), which can lead to decreased efficacy of cefazolin in some isolates, is a concern, but recent data suggest similar efficacy or even a trend towards superiority of cefazolin over antistaphylococcal penicillins 1.
Treatment Approach
- Cefazolin is recommended for treatment of pyomyositis caused by MSSA, and can be used for MSSA bacteremia 1.
- Vancomycin may be used empirically while awaiting susceptibility results, but beta-lactam therapy (such as cefazolin) is preferred for MSSA bacteremia 1.
- Duration of therapy is typically 2-3 weeks, but may vary depending on the individual patient and the presence of complications 1.
From the Research
Treatment for Persistent Methicillin-Sensitive Staphylococcus aureus (MSSA) Bacteremia
- The combination of Cefazolin and Ertapenem has been shown to be an effective salvage regimen for refractory methicillin-susceptible Staphylococcus aureus bacteremia 2, 3, 4, 5.
- Studies have demonstrated that Cefazolin plus Ertapenem can rapidly clear persistent MSSA bacteremia, including immediate clearance (≤24 hours) in some cases 3.
- The combination of Cefazolin and Ertapenem has been found to exhibit synergistic action in a rat model of MSSA endocarditis, and in vitro studies have shown bactericidal activity against MSSA biofilms 3, 4, 5.
- Ertapenem has been shown to reduce the concentrations of Cefazolin required to eradicate MSSA biofilms to those achievable in vivo by standard dosing, translating into shorter bacteremia duration in patients with MSSA endocarditis 4.
- Cefazolin has been considered as an alternative to antistaphylococcal penicillins for the treatment of MSSA bacteremia, offering several pharmacologic advantages, including more convenient dosing regimens 6.
Key Findings
- The combination of Cefazolin and Ertapenem has been found to be effective in clearing persistent MSSA bacteremia, including in cases of endocarditis 3, 4, 5.
- In vitro studies have demonstrated synergistic action between Cefazolin and Ertapenem against MSSA, including against biofilms 4, 5.
- Clinical studies have suggested similar clinical efficacy but better tolerability of Cefazolin compared with antistaphylococcal penicillins for the treatment of MSSA bacteremia 6.