Oral step-down for Staphylococcus aureus bacteraemia: an opportunity for antimicrobial stewardship?

Long courses of intravenous antimicrobial therapy are traditionally recommended for the treatment of methicillin sensitive Staphylococcus aureus bacteraemia (MS-SAB), but are not always completed in clinical practice. Early intravenous to oral antibiotic switch is a key component of antimicrobial stewardship. This study aimed to identify whether intravenous antibiotic duration may be safely reduced in MS-SAB.

We performed a single-centre retrospective study of MS-SAB management. Successful outcome was defined as 90-day recurrence-free survival. Effect of intravenous antibiotic duration on 90-day recurrence risk was examined.

281 adult cases of MS-SAB were evaluated, of which 208 (74%) had a successful outcome. 176 cases (63%) received less than 14 days of intravenous antimicrobial therapy. Very short durations of intravenous therapy were associated with increased risk of recurrence (<7 days iv, 9.8% recurrence; 7-13 days, 1.4%; ≥14 days, 2.9%; p 0.005). This effect was robust to sensitivity analysis for total antimicrobial therapy duration of 14 days. CRP reduction of at least 37% from peak value at intravenous to oral antibiotic switch was associated with decreased risk of recurrence (<37% CRP reduction, 12% recurrence; >37%, 2.0%; p 0.001).

Oral antimicrobial switch may allow safe reductions in duration of intravenous therapy in MS-SAB.