From the Guidelines
Persistent MSSA bacteremia should be treated with intravenous cefazolin or an anti-staphylococcal penicillin (ASP) for at least 4-6 weeks, with a strong emphasis on early source control and infectious disease consultation. The treatment approach should prioritize morbidity, mortality, and quality of life outcomes. According to the most recent and highest quality study 1, the use of cefazolin or an ASP is recommended for MSSA bacteremia.
Key Considerations
- Early source control is crucial, including removing infected intravascular devices, draining abscesses, and debriding infected tissues 1.
- Treatment duration should be at least 4-6 weeks for complicated bacteremia, measured from the first negative blood culture 1.
- Echocardiography is essential to rule out endocarditis, and repeat blood cultures every 24-48 hours until clearance is documented.
- Infectious disease consultation is strongly recommended for persistent bacteremia cases.
Antibiotic Choice
- Cefazolin or an ASP, such as nafcillin or oxacillin, is the recommended first-line treatment for MSSA bacteremia 1.
- Vancomycin or daptomycin may be considered for MRSA bacteremia, but this is not relevant to MSSA cases 1.
Monitoring and Adjustments
- Repeat imaging studies should be performed in patients with persistent bacteremia to identify undrained foci of infection 1.
- Antibiotics should be administered intravenously initially, but oral antibiotics may be appropriate for patients with prompt clearance of bacteremia and no evidence of endocarditis or metastatic abscess 1.
From the FDA Drug Label
The overall Adjudication Committee success rates in the ITT population were 44. 2% (53/120) in patients treated with daptomycin for injection and 41.7% (48/115) in patients treated with comparator (difference = 2.4% [95% CI −10.2,15.1]). Among patients with persisting or relapsing S. aureus infections, 8/19 daptomycin for injection-treated patients and 7/11 comparator-treated patients died Failure of treatment due to persisting or relapsing S aureus infections was assessed by the Adjudication Committee in 19/120 (16%) daptomycin for injection-treated patients (12 with MRSA and 7 with MSSA) and 11/115 (10%) comparator-treated patients (9 with MRSA treated with vancomycin and 2 with MSSA treated with an anti-staphylococcal semi-synthetic penicillin) The median time to clearance in patients with MSSA was 4 days and in patients with MRSA was 8 days. Most patients who failed due to persisting or relapsing S aureus infection had deep-seated infection and did not receive necessary surgical intervention
The treatment of persistent MSSA bacteremia with daptomycin is associated with a success rate of 45% in patients with MSSA.
- The median time to clearance of MSSA bacteremia is 4 days.
- Failure of treatment due to persisting or relapsing S aureus infections occurred in 7/120 (6%) daptomycin for injection-treated patients with MSSA.
- Surgical intervention is necessary for patients with deep-seated infection. 2
From the Research
Treatment Options for Persistent MSSA Bacteremia
- Cefazolin is considered a viable alternative to antistaphylococcal penicillins (ASPs) for the treatment of MSSA bacteremia, offering more convenient dosing regimens and better tolerability 3.
- Studies have shown that cefazolin has similar clinical efficacy to ASPs, with lower rates of discontinuation due to adverse drug reactions 3, 4, 5.
- Daptomycin may also be a comparable alternative to ASBLs for the treatment of MSSA bacteremia, with no differences in clinical outcomes identified in a single-center retrospective cohort study 6.
- A narrative review of therapeutic options for adult patients with persistent MSSA bacteremia found that modification of antimicrobial therapy, in conjunction with source control and infectious diseases consultation, may be necessary to sterilize blood cultures 7.
Comparison of Cefazolin and Antistaphylococcal Penicillins
- A meta-analysis found that cefazolin was associated with lower 90-day mortality and fewer discontinuations due to adverse events compared to ASPs 5.
- A nationwide cohort study found that patients who received cefazolin had a 37% reduction in 30-day mortality and a 23% reduction in 90-day mortality compared to patients receiving nafcillin or oxacillin 4.
- A comparative review of cefazolin versus ASPs found that cefazolin offered several pharmacologic advantages, including more convenient dosing regimens, and was increasingly being used as the preferential agent for MSSA infections as part of cost-saving initiatives 3.
Considerations for Treatment
- Source control, such as intravascular catheter removal, debridement, or drainage, is crucial in the treatment of MSSA bacteremia 3, 7.
- Aggressive cefazolin dosing may help mitigate the role of cefazolin inoculum effect and improve clinical outcomes 3.
- Infectious diseases consultation may be necessary to guide treatment decisions and optimize outcomes 7.