1707. In vitro Activities of Ceftazidime-Avibactam and Comparator Agents against Enterobacterales and Pseudomonas aeruginosa Collected < 48 Hours and ≥48 Hours Post-Admission from Hospitalized Adult Patients, ATLAS Global Surveillance Program 2017-2020

Abstract

Abstract Background Effective treatments for Gram-negative infections have dwindled with the emergence and dissemination of multi-drug resistant Enterobacterales (Ent) and Pseudomonas aeruginosa (Psa). Fortunately, ceftazidime-avibactam (CAZ-AVI) has activity against Ent and Psa isolates that produce Class A, C and some Class D β-lactamases. This study examined the in vitro activity of CAZ-AVI and comparators against Ent and Psa from presumed community-acquired (CA; cultured < 48 h after hospital admission) and hospital-acquired (HA; cultured ≥48 h post-admission) infections collected from adult patients as part of the ATLAS surveillance program, 2017-2020. Methods 59,904 non-duplicate Ent and 2,504 Psa isolates from adult patients (≥18 y.o.) were collected from 271 sites in 57 countries as part of ATLAS 2017-2020 (excluding North America) for which the length of hospitalization stay was specified. Antimicrobial susceptibility testing was by broth microdilution according to CLSI guidelines and analyzed using CLSI 2022 breakpoints. Ent isolates testing with meropenem MICs >1 µg/mL and Escherichia coli, Klebsiella pneumoniae, K. oxytoca, K. variicola, and Proteus mirabilis testing with ceftazidime and/or aztreonam MICs >1 mg/L were genetically screened for β-lactamases. For Psa, meropenem MIC >2 µg/mL triggered β-lactamase screening. In 2020, approximately 25% of the meropenem non-susceptible isolates were screened. Results For Ent, CAZ-AVI was the most active agent examined against both the CA- and HA-infection population of isolates. The percentage of Ent isolates susceptible to CAZ-AVI was 2.6% and 5.3% higher compared to meropenem for the CA- and HA-infection sets, respectively. Considering both the CA- and HA- infection Psa isolates, CAZ-AVI was also the most active agent among comparators, showing %S rates 12.8% and 19.3% higher than meropenem, respectively. Conclusion Against Ent and Psa from adult patients, CAZ-AVI exhibited excellent in vitro activity regardless of whether the pathogen was isolated < 48 hrs. or ≥48 hrs. post hospital admission. The slightly decreased susceptibility to CAZ-AVI for the HA Psa isolates as compared to the CA isolates, as well as the relatively low %S rates for comparators, reinforces difficult-to-treat nature of nosocomial infections. Disclosures All Authors: No reported disclosures.