Impact of the use of aminoglycosides in combination antibiotic therapy on septic shock and mortality due to Staphylococcus aureus bacteremia

Abstract

Background The purpose of this study was to evaluate the possible impact of antimicrobial combination regimens containing an aminoglycoside (AG) on morbidity and mortality associated with S. aureus bacteremia. Methods All inpatients over 18 years of age with S. aureus bacteremia were prospectively enrolled in three tertiary care hospitals in France and Ireland. Patients were included in the group “treated with AG” if they received at least 24 h of aminoglycoside therapy within 7 days after a positive blood culture in combination with an effective antimicrobial against the S. aureus. A Cox's proportional hazard model was used in univariate and multivariate survival analysis, the covariate “treatment with AG” being introduced as a time-dependent covariate. Results Nine percent of the 90 patients who received AG died because of infection versus 13% in the group that did not receive a combination including an AG ( p > 0.05). In the multivariate Cox model, stratified by septic shock and controlling for age and Charlson-weighted index of comorbidity, the adjusted odds ratio for death due to S. aureus infection associated with the use of AG was 0.6 [95% CI: (0.2–1.9); p = 0.4]. However, AG was found to have a protective effect on septic shock occurrence [OR = 0.3; 95% CI: (0.1–0.7), p = 0.004], controlling for age, portal of entry not related to catheter infection, and diabetes. Conclusion Although there was no decrease in mortality due to S. aureus infection in patients treated with AG therapy, we found a significant benefit of AG in preventing septic shock. This data argues for the early use of AG in patients with S. aureus bacteremia.