Abstract

Background: Clinical justification for rapid antimicrobial susceptibility testing (AST) in Gram-negative rod (GNR) bacteremia is compelling; however, evidence supporting its value is sparse. We investigated the impact of rapid AST on clinical and antimicrobial stewardship outcomes in real-world practice.Methods: We performed a before and after quasi-experimental study from February 2018 to July 2019 at a tertiary hospital of the 24-hour/day, 7-day/week implementation of the direct VITEK2 AST method from positive blood culture broth for GNR bacteremia with electronic isolate-specific de-escalation comments, and daytime antibiotic stewardship program (ASP) intervention. The primary outcome was time to appropriate antibiotic escalation or de-escalation, and secondary outcomes included time to oral antibiotic step-down, hospital length-of-stay (LOS), all-cause 30-day mortality, 7-day incidence of acute kidney injury (AKI) and 30-day incidence of C. difficile infection (CDI).Results: A total of 671 GNR isolates were included from 643 adult patients. Among patients for whom antibiotic change occurred after rapid AST result, rapid AST was associated with a trend in decreased time to escalation or de-escalation (hazard ratio 1.22, 95% CI 0.99-1.51; p=0.06), with median times of 52.3 vs 42.2 hours. Secondary outcomes were similar in both groups including median time to oral antibiotic step-down, LOS, all-cause mortality, and incidence of AKI and CDI.Conclusion: Rapid AST led to improved stewardship measures but did not impact clinical patient outcomes. These results highlight that multiple variables in addition to timing of AST result contribute to clinical outcome and that further intervention may be required to clinically justify rapid AST implementation.

View details for DOI 10.1128/JCM.00360-20

View details for PubMedID 32434782