644. Activity of Meropenem-Vaborbactam and Comparators Against Isolates from Patients in Hematology/Oncology and Transplant Units in the United States

Abstract Background Patients undergoing treatment for cancer or an organ transplant are often immunosuppressed and particularly susceptible to infections caused by Gram-negative pathogens, including resistant isolates. Meropenem-vaborbactam is a combination of carbapenem beta-lactamase inhibitor that effective against serine-beta-lactamases, KPC carbapenemase. We evaluated the activity meropenem-vaborbactam (MEV) comparators Enterobacterales isolates collected in US during 2014-2021 from patients hematology, oncology, units (H/T). Activity comparator antimicrobial agents tested CRE medical centers Methods A total 2,185 clinical were consecutively H/T 33 hospitals all 9 Census Divisions. Isolates using CLSI broth microdilution methodology. Results interpreted breakpoints. Carbapenem-resistant (CRE) characterized as having MIC values ≥ 4 mg/L imipenem and/or meropenem (MER). subset CREs genotypically carbapenemase genes PCR whole genome sequencing. The most common species isolated Escherichia coli (n=863), Klebsiella pneumoniae (n=518), Enterobacter cloacae complex (n=284). infection type was bloodstream (n=1,057), followed urinary tract (n=347). Susceptibility 99.6% MEV, 98.5% MER, 83.4% piperacillin-tazobactam (Table). 28 (1.3%) CRE; susceptibility these MEV 71.4% while their susceptibilities levofloxacin 25.0% 0.0%, respectively Of CRE, 19 characterized. 13 produced KPC, 3 OXA-48/232, 1 had NDM-5. All KPC-producing susceptible, OXA-48/232 NDM resistant. Conclusion very active causing patients, CREs. These vitro data suggest would be option with infections. Disclosures Dee Shortridge, PhD, AbbVie: Grant/Research Support|JMI Laboratory: Employee|Melinta: Support|Menarini: Support|Shionogi: Support Lalitagauri M. Deshpande, Melinta: Support|Pfizer: Cecilia G. Carvalhaes, MD, Support|Cidara: Support|Melinta: Mariana Castanheira, Support|GSK: Support.