1568. In Vitro Activity of Ceftazidime-Avibactam and Comparator Agents Against Enterobacterales and Pseudomonas aeruginosa Collected < 48 Hours and ≥48 Hours Post-Admission from Pediatric Patients, ATLAS Surveillance Program 2015-2018

BACKGROUND: Ceftazidime-avibactam (CAZ-AVI) is a β-lactam/non-β-lactam β-lactamase inhibitor combination with in vitro activity against Enterobacterales (Ent) and Pseudomonas aeruginosa (Psa) carrying Class A, C and some Class D β-lactamases. We examined the in vitro activity of CAZ-AVI and comparators against presumed community-acquired (CA; cultured < 48 h after hospital admission) and hospital-acquired (HA; cultured ≥48 h post-admission) isolates collected from pediatric patients as part of the ATLAS surveillance program. METHODS: 6023 non-duplicate isolates were collected in 50 countries in Europe (n=3122), Latin America (n=1220), Middle East/Africa (n=1007), and Asia/Pacific (excluding China; n=674) from patients (newborn to 17 y) with lower respiratory tract (LRTI; n=1641), urinary tract (UTI; n=1595), skin and soft tissue (SSTI; n=1027), intra-abdominal (IAI; n=949), and bloodstream (BSI; n=811) infections. Susceptibility testing was performed by CLSI broth microdilution and values were interpreted using CLSI 2020 breakpoints. CAZ-AVI was tested at a fixed concentration of 4 µg/mL AVI. Isolates with CAZ or aztreonam MICs ≥2 µg/mL (Escherichia coli, Klebsiella spp., Proteus mirabilis) or meropenem MICs ≥2 µg/mL (all Ent species) or ≥4 µg/mL (Psa) were screened for β-lactamase genes. RESULTS: The in vitro activity of CAZ-AVI exceeded that of meropenem and other tested β-lactams against Ent (98.5% susceptible (S)) and Psa (93.1% S) collected globally from pediatric patients (Table). Percentages of susceptibility to CAZ-AVI ranged from 96.8-99.3% among CA Ent from different infection types and were reduced 0.4-1.0% among HA isolates from SSTI, IAI and BSI. Susceptibility to CAZ-AVI was also similar (92.7-95.4% S) among CA Psa from different infection types and was reduced 0.1-4.4% among HA isolates. For both Ent and Psa, the lowest percentages of susceptibility to the tested β-lactams were observed among isolates from BSI, which included a higher proportion of isolates carrying extended-spectrum β-lactamases and/or carbapenemases than isolates from other infection types. Table [Image: see text] CONCLUSION: CAZ-AVI could provide a valuable therapeutic option for treatment of CA and HA infections caused by Ent and Psa in pediatric patients. DISCLOSURES: Krystyna Kazmierczak, PhD, IHMA (Employee)Pfizer, Inc. (Consultant) Greg Stone, PhD, AztraZeneca (Shareholder, Former Employee)Pfizer, Inc. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor)