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

Abstract

Objectives: 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.

Methods: 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.

Results: 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).

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

Keywords: Staphylococcus aureus; antimicrobial stewardship; bacteraemia.

Fig. 1

Intravenous to oral antimicrobial therapy switch and probability of recurrence. A. Very short duration intravenous antibiotic therapy (<7 days) was associated with increased risk of recurrent MS-SAB within 90 days. Durations of 7–13 days showed no increased risk compared with ≥14 days. B. Total duration of antimicrobial therapy (intravenous plus oral) of less than 14 days was associated with upper confidence limit exceeding 10 %. C. Low CRP ratio (reduction of at least 37 % from peak value) was associated with reduced risk of recurrence. Dark dots show whole dataset. Pale dots show sensitivity analyses. Error bars show one-sided 95 % binomial CI. Dotted lines show expected range of MS-SAB recurrence rate (5–10 %).

Fig. 2

Oral antimicrobial follow-on agents in MS-SAB. Follow-on oral anti-staphylococcal therapy after initial intravenous therapy (n = 172). Where more than one oral anti-staphylococcal agent used, the agent used immediately after intravenous to oral switch is shown. BL, beta-lactam; BL(dual), dual oral antimicrobial therapy including a BL; CLI, clindamycin; LZD, linezolid; other(dual), dual oral antimicrobial therapy not including a BL, CLI or LZD.