Antibiotic appropriateness for Gram-negative bloodstream infections: impact of infectious disease consultation.

Background: We investigated the role of infectious disease consultation (IDC) on therapeutic appropriateness in Gram-negative bloodstream infections (GNBSIs) in a setting with a high proportion of antibiotic resistance. Secondary outcomes were in-hospital mortality and the impact of rapid diagnostic tests (RDTs).

Methods: Retrospective study on hospitalised patients with GNBSIs. Therapy was deemed appropriate if it had the narrowest spectrum considering infection and patients' characteristics. Interventional-IDC (I-IDC) group included patients with IDC-advised first appropriate or last non-appropriate therapy. Time to first appropriate therapy and survival were evaluated by Kaplan-Meier curves. Factors associated with therapy appropriateness were assessed by multivariate Cox proportional-hazard models.

Results: 471 patients were included. High antibiotic resistance rates were detected: quinolones 45.5%, third-generation cephalosporins 37.4%, carbapenems 7.9%. I-IDC was performed in 31.6% of patients (149/471), RDTs in 70.7% (333/471). The 7-day probability of appropriate treatment was 91.9% (95% confidence interval [95%CI]: 86.4-95.8%) vs. 75.8% (95%CI: 70.9-80.4%) with and without I-IDC, respectively (-value = 0.0495); 85.5% (95%CI: 81.3-89.1%) vs. 69.4% (95%CI: 61.3-77.2%) with and without RDTs, respectively (-value = 0.0023). Compared to RDTs alone, the combination with I-IDC was associated with a higher proportion of appropriate therapies at day 7: 81.9% (95%CI: 76.4-86.7%) vs. 92.6% (95%CI: 86.3-96.7%). At multivariate analysis, I-IDC and RDTs were associated with time to first appropriate therapy [adjusted hazard-ratio 1.292 (95%CI: 1.014-1.647) and 1.383 (95%CI: 1.080-1.771), respectively], with no impact on mortality.

Conclusions: In a setting with a high proportion of antibiotic resistance, IDC and RDTs were associated with earlier prescription of appropriate therapy in GNBSIs, without impact on mortality.