What is the treatment for Methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia with an oral source?

From the Guidelines

For MSSA bacteremia, the recommended treatment includes the use of cefazolin or an anti-staphylococcal penicillin (ASP) as the primary antibiotic choice. When considering oral step-down therapy for MSSA bacteremia, it is crucial to prioritize the most effective and recent evidence-based practices. According to the study published in Clinical Infectious Diseases in 2023 1, the use of cefazolin or an anti-staphylococcal penicillin (ASP) is recommended for MSSA.

Key Considerations

• Early source control is essential in the management of MSSA bacteremia.
• The treatment duration should be 4–6 weeks for bacteremia with high-risk features.
• Oral step-down therapy may be considered after initial intravenous therapy, depending on the clinical response and presence of complications.

Antibiotic Choice

The choice of antibiotic is critical in the treatment of MSSA bacteremia. Cefazolin or an anti-staphylococcal penicillin (ASP) are the preferred options due to their effectiveness against MSSA, as noted in the 2023 study 1.

Treatment Approach

The treatment approach should include:

• Initial intravenous antibiotic therapy with cefazolin or an ASP.
• Early source control to prevent reinfection.
• Consideration of oral step-down therapy after initial intravenous therapy, depending on the clinical response and presence of complications.
• Total treatment duration of 4-6 weeks for bacteremia with high-risk features.

From the FDA Drug Label

The clinical success rates determined at 7 to 14 days after last dose of therapy (IV and oral) (TOC visit) were 88% (45/51) for daptomycin for injection and 77% (17/22) for comparator The FDA drug label does not answer the question about MSSA bacteremia oral treatment, as the provided text only discusses intravenous (IV) treatment with daptomycin and does not provide information on oral treatment options for MSSA bacteremia. 2

From the Research

MSSA Bacteremia Oral Treatment

• The treatment of Methicillin-Susceptible Staphylococcus aureus (MSSA) bacteremia typically involves the use of anti-staphylococcal beta-lactams, with cefazolin and nafcillin or oxacillin being commonly recommended options 3, 4, 5.
• A study comparing cefazolin to nafcillin or oxacillin for the treatment of MSSA infections complicated by bacteremia found that patients who received cefazolin had a lower risk of mortality and similar odds of recurrent infections 5.
• Another study found that cefazolin is not significantly different from cloxacillin in the treatment of MSSA bacteremia, while treatment with other beta-lactams, including second and third generation cephalosporins, might be associated with higher mortality 3.
• The use of oral antibiotics for the treatment of MSSA bacteremia is not well established, but a study suggested that oral step-down therapy may be a viable option for patients with MSSA bacteremia, allowing for safe reductions in the duration of intravenous therapy 6.
• The choice of antibiotic therapy for MSSA bacteremia should be guided by the results of susceptibility testing, with cefazolin or antistaphylococcal penicillins being recommended for MSSA 4.

Oral Antibiotics for MSSA Bacteremia

• There is limited evidence to support the use of oral antibiotics as a first-line treatment for MSSA bacteremia, but oral step-down therapy may be considered in certain cases 6.
• A study found that CRP reduction of at least 37% from peak value at intravenous to oral antibiotic switch was associated with decreased risk of recurrence in patients with MSSA bacteremia 6.
• The use of oral antibiotics for the treatment of MSSA bacteremia should be guided by the results of susceptibility testing and the clinical judgment of the treating physician 4.

Treatment Duration and Recurrence

• A study found that very short durations of intravenous therapy (<7 days) were associated with increased risk of recurrence in patients with MSSA bacteremia, while durations of 7-13 days and ≥14 days were associated with lower risks of recurrence 6.
• The optimal duration of antibiotic therapy for MSSA bacteremia is not well established, but it is generally recommended that treatment be continued for at least 14 days 4.
• The risk of recurrence in patients with MSSA bacteremia can be reduced by ensuring adequate treatment duration and by using oral step-down therapy in certain cases 6.