Impact of the presence of a prosthetic implant and transition to oral stepdown therapy on relapse rates and mortality in uncomplicated <i>Staphylococcus aureus</i> bacteremia treated with 14 days of antibiotics: a retrospective cohort study

The aim of this single-center, retrospective observational study was to evaluate the effects of having a prosthetic implant (PI) and of changing from intravenous to oral antibiotics (oral stepdown therapy [OST]) on the risk of relapse in patients with otherwise uncomplicated <i>Staphylococcus aureus</i> bacteremia (SAB) treated with antibiotics for 14 days. The primary outcome was the 90-day SAB relapse rate in patients with and without a PI. Secondary outcomes were 90-day mortality among patients with or without a PI and 90-day SAB relapse and mortality in patients who had OST. We included 188 consecutive patients with SAB without metastatic foci and with a planned antibiotic treatment duration of 14 days: 58 (31%) had a presumed uninfected PI, and 108 (57%) had OST. Four patients (2%) relapsed, and 25 patients (13%) died. Patients with a PI were more likely to have diagnostic tests performed. In the univariate analysis, the presence of a PI (odds ratio [OR] 7 [95% confidence interval {CI} 0.9-144.0]) and OST (OR 0.7 [95% CI 0.1-6.2]) were not associated with 90-day relapse. In the multivariable analysis, the presence of a PI (adjusted odds ratio [aOR] 1.3 [95% CI 0.5-3.7]) and OST (aOR 0.5 [95% CI 0.2-1.4]) were not predictive of 90-day mortality. In a setting where full diagnostic workup and close follow-up can be ensured, the presence of a PI and OST did not seem to be associated with an increase in 90-day mortality in patients with otherwise uncomplicated SAB. Although the relapse rate was low overall, there was a non-significant trend toward a higher risk of relapse in patients with a PI.IMPORTANCEThis retrospective study provides reassuring real-world data supporting a short 14-day treatment course for SAB in patients with PIs. In an era of increasing antimicrobial resistance worldwide, these retrospective findings support the perspective that not all PIs are systematically infected. Prolonged antibiotic therapy may therefore not be routinely needed if infection is excluded and thorough evaluation for dissemination performed, accompanied by close clinical and biological monitoring. Early transition to oral therapy in this context, which has been implemented in our institution for years, does not appear to be associated with a higher risk of therapeutic failure. These findings align with the most recent literature on the subject.