409. Temporal Trends in Antibiotic Use of New β-lactams for Gram-Negative Bacteria with Difficult-to-Treat Resistance in the Southeastern United States

Abstract Background Several new β-lactam antibiotics were recently developed for treatment of serious infections due to gram-negative bacteria (GNB) with difficult-to-treat resistance (DTR). This multicenter retrospective cohort study examined temporal trends in prevalence GNB DTR and the use β-lactams southeastern United States. Methods The DTR, including Enterobacterales, Pseudomonas aeruginosa, Acinetobacter species was determined 9 hospitals geographically spread within Southeastern Research Group Endeavor (SERGE-45) between 2015 2020. Antibiotic (AU) also obtained from during period. New included ceftolozane/tazobactam, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/cilastatin/relebactam, cefiderocol. Logistic regression analysis utilized examine cumulative AU β-lactams. Results overall 0.78% a numerical increase 0.67% 0.97% 2020 (p=0.067) [Figure]. more prevalent among spp., followed by P. Enterobacterales (11.8%, 3.5%, 0.2%, respectively). There significant isolates spp. 2.7% 20.7% (p< 0.001) 0.07% 2.6% (p=0.025), but not aeruginosa (p=0.46) 2 days therapy per 1000 patient-days. these agents 0.03 2.22 patient 6-year period (p=0.096) Conclusion remain relatively low However, upward trend isolates, particularly is concerning may drive future increased Additional efforts benchmark appropriateness are crucial preserve their efficacy against DTR. Disclosures Brandon Bookstaver, PharmD, Spero Therapeutics: Advisor/Consultant Julie Ann Justo, MS, FIDSA, BCPS-AQ ID, bioMerieux: Honoraria|bioMerieux: Honoraria|Entasis Advisor/Consultant|Entasis Advisor/Consultant|Gilead Sciences: Advisor/Consultant|Merck & Co: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi Inc.: Advisor/Consultant|Spero Honoraria|Spero Honoraria|Vaxart: Stocks/Bonds Bruce M. Jones, Pharm.D., BCPS, AbbVie: Advisor/Consultant|AbbVie: Honoraria|La Jolla: Honoraria|Melinta: Advisor/Consultant|Paratek: Honoraria|Regeneron: Honoraria.