1811. Minimizing Time to Optimal Therapy for Enterobacteriaceae Bloodstream Infections: Is Organism Identification Enough?

BACKGROUND: BSI due to ceftriaxone (CRO)-resistant ENT are increasing in frequency, and are associated with delays in time to appropriate therapy. However, treating all patients at risk for CRO-resistant organisms with empiric carbapenem (CARB) therapy risks over exposure. Strategies are needed to appropriately balance these competing interests. The purpose of this study was to compare three methods for accomplishing this balance. METHODS: Retrospective observational study of patients at the Detroit Medical Center with ENT BSI from July 1, 2016 to July 31, 2017. Patients with E. coli, K. oxytoca, K. pneumoniae, or P. mirabilis were included if both Verigene® GN-BC and traditional microbiology detected the organism. Patients were excluded if CARB resistance was detected via genetic markers. This study assessed the effectiveness of three methods to predict CRO resistance at the time of organism isolation. The first two methods were based on applying published scoring tools for extended spectrum β-lactamase BSI. If the patient met the cutoff score proposed by the authors they were hypothetically placed on a CARB, otherwise they were placed on CRO. Method 3 was based on results from Verigene. If the CTX-M marker was present patients were hypothetically placed on a CARB, and if not CRO. The methods were compared for their sensitivity, specificity, predictive values, and the number of times they would have resulted in inappropriate therapy or unnecessary escalation to CARB. RESULTS: Four hundred fifty-one ENT were included, 73 (16%) of which were CRO-resistant. The comparative performance of the three methods is listed in the figure. Verigene performed well and was associated with fewer cases of early under treatment and over treatment. Published ESBL scoring tools performed poorly, missing two-thirds of CRO-resistant isolates and unnecessarily exposing many patients to CARB. Given the improved sensitivity and specificity of Verigene similar overall CARB use would be seen in the cohort despite roughly 40 patients getting placed on CARB 2 days earlier when CRO-resistant BSI was present. CONCLUSION: Vergiene significantly outperformed published ESBL scoring tools for identifying CRO-resistant ENT BSI. Institutions should validate scoring tools prior to implementation. [Image: see text] DISCLOSURES: T. T. Timbrook, BioFire Diagnostics: Scientific Advisor, Speaker honorarium. Roche Diagnostic: Scientific Advisor, Speaker honorarium. GenMark Diagnostics: Scientific Advisor, Speaker honorarium.