Kaasch AJ, Rieg S, Kuetscher J, Brodt HR, Widmann T, Herrmann M, Meyer C, Welte T, Kern P, Haars U, Reuter S, Hübner I, Strauss R, Sinha B, Brunkhorst FM, Hellmich M, Fätkenheuer G, Kern WV, and Seifert H
Objectives: Early broad-spectrum antimicrobial treatment reduces mortality in patients with septic shock. In a multicenter, prospective observational study, we explored whether delayed appropriate antimicrobial therapy (AAT) influences outcome in Staphylococcus aureus bloodstream infection (SAB)., Methods: Two hundred and fifty-six patients with SAB from ten German study centers were enrolled and followed for 3 months. Predisposing factors, clinical features, diagnostic procedures, antimicrobial therapy, and outcome were recorded. The appropriateness of antimicrobial therapy was judged by a trained physician based on in vitro activity, dosage, and duration of therapy. Therapy was considered to be delayed when more than 24 h elapsed between the first positive blood culture and the start of appropriate therapy. The association of delayed therapy with overall mortality and SAB-related events (i.e., attributable mortality or late SAB-related complications) was assessed by crosstabulation and propensity score-based logistic regression., Results: One hundred and sixty-eight patients received AAT during their hospital stay, of whom 42 (25%) received delayed AAT. The overall mortality and the occurrence of severe sepsis or septic shock were lower in patients with delayed AAT, pointing towards confounding by indication. Adjusted 90-day mortality (adjusted odds ratio [OR] 0.91, 95% confidence interval [CI] [0.39-2.13], p 0.82) and SAB-related events (adjusted OR 1.46, 95% CI [0.47-4.51], p 0.52) also failed to show a significant impact of delayed AAT on outcome., Conclusion: In patients with SAB, early AAT may not improve survival. However, confounding by indication is a major challenge when analyzing and interpreting observational studies on the impact of delayed AAT.