What is the treatment for persistent Methicillin-Sensitive Staphylococcus aureus (MSSA) bacteremia?

From the Guidelines

Treatment for Persistent MSSA Bacteremia

The treatment for persistent Methicillin-Sensitive Staphylococcus aureus (MSSA) bacteremia involves the use of antistaphylococcal penicillins such as nafcillin or oxacillin, or first-generation cephalosporins like cefazolin 1.

• Key considerations include:
  • Cefazolin or antistaphylococcal penicillin (eg, nafcillin or oxacillin) is recommended for treatment of infections caused by MSSA 1.
  • Early drainage of purulent material should be performed to help clear the infection source 1.
  • Repeat imaging studies should be performed in patients with persistent bacteremia to identify undrained foci of infection 1.
  • Antibiotics should be administered intravenously initially, with a switch to oral antibiotics possible once the patient is clinically improved, provided there's no evidence of endocarditis or metastatic abscess 1.
  • A minimum treatment duration of 2 to 3 weeks is recommended, but this may need to be extended based on clinical response and the presence of complicating factors such as endocarditis or metastatic infections 1.
• It's crucial to tailor the treatment based on the patient's clinical response, the presence of any complicating factors, and the results of cultures and sensitivity testing.
• In clinical practice, the choice between nafcillin, oxacillin, and cefazolin may depend on factors such as the patient's renal function, the presence of any allergies to penicillins or cephalosporins, and local resistance patterns.
• For patients who cannot tolerate these first-line treatments, alternative antibiotics may be considered, but the choice should be guided by susceptibility testing and clinical experience.

From the FDA Drug Label

The median time to clearance in patients with MSSA was 4 days and in patients with MRSA was 8 days. 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 treatment for persistent Methicillin-Sensitive Staphylococcus aureus (MSSA) bacteremia is not explicitly stated in the provided drug label. However, based on the information provided, anti-staphylococcal semi-synthetic penicillin (such as nafcillin, oxacillin, cloxacillin, or flucloxacillin) is used as a comparator in the study, suggesting it may be a potential treatment option.

• Key points:
  • Median time to clearance of MSSA bacteremia was 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
  • Anti-staphylococcal semi-synthetic penicillin was used as a comparator in the study 2

From the Research

Treatment Options for Persistent Methicillin-Sensitive Staphylococcus aureus (MSSA) Bacteremia

• The preferred management of patients with MSSA bacteremia includes definitive therapy with intravenous anti-staphylococcal beta-lactam (ASBL) antibiotics, such as nafcillin or cefazolin 3.
• Daptomycin may serve as a comparable alternative to ASBLs for treatment of MSSA bacteremia, as no differences in clinical outcomes were identified in a single-center retrospective cohort study 3.
• Cefazolin has been shown to have a lower risk of mortality and similar odds of recurrent infections compared to nafcillin or oxacillin for MSSA infections complicated by bacteremia 4.
• Ceftriaxone has been evaluated as a potential treatment option for MSSA infections, with current evidence suggesting no difference in efficacy between ceftriaxone and ASAs, but a lower risk of toxicity with ceftriaxone 5.

Adjunctive Therapy

• The use of adjunctive daptomycin in the treatment of MSSA bacteremia has been investigated, but a randomized, controlled trial found that it did not shorten the duration of bacteremia and should not be routinely considered 6.

Considerations for Treatment

• The choice of treatment for MSSA bacteremia should be based on individual patient factors, such as allergy or intolerance to beta-lactam antibiotics, and the severity of the infection 3, 4.
• Further studies are needed to establish the optimal treatment regimen for MSSA bacteremia and to compare the effectiveness of different treatment options 3, 4, 5.