653. Characterizing Antibacterial Regimen Modification, Patient Characteristics, and Outcomes for Patients with Complicated Gram-negative Bacterial Infections

Abstract Background There are few studies describing the rationale or frequency of empiric or directed therapy treatment modification behaviors among patients with complicated Gram-negative bacterial infections (GNBI). We sought to characterize patient and treatment characteristics, details of regimen modification, and patient outcomes. Methods This retrospective chart review included patients, admitted from 1/1/2019-12/31/2020 to Hoag Memorial Hospital, with a complicated GNBI due to an extended spectrum cephalosporin resistant pathogen. We present an interim descriptive analysis of 60 patients: demographics, ABX modifications, rationale and timing for modifications, and patient outcomes. ABX modifications were defined a GNB ABX switched, added, or removed. Results The predominant culture sources were urine and bloodstream. ESBL organisms (38%) and Pseudomonas spp (32%) were most common. Inpatient initial empiric therapies included TZP (33%), MEM (20%), and CRO (17%). 32% of patients did not have any modifications to their ABX regimens. For patients where modifications occurred this ranged from 0 to 6 changes. Time to the first modification ranged from 2 – 196 hours. For initial modifications, all were considered escalations, and most were based on preliminary culture results (36%), lack of patient response (28%), additional history review (28%) and decompensation (1.7%). No difference in 30 or 90-day mortality or 90-day readmission was observed for patients that did or did not have ABX modifications. Conclusion Many patients experience modification to GNB targeted antibacterials, in almost all cases, rationale for change was documented. In this interim analysis no difference in patient outcomes was observed. However, it is well established that increased duration of therapy and exposure to numerous antibacterial agents can increase healthcare resource utilization and may negatively impact local ecology, respectively. Disclosures Jason Yamaki, PharmD, PhD, Merck & Co. Inc.,: Grant/Research Support Ryan J. Dillon, MSc, Merck: Employee|Merck: Stocks/Bonds.