1261. Antimicrobial Activity of Aztreonam-Avibactam against Gram-negative Bacteria Isolated from Patients Hospitalized with Pneumonia in Europe, Latin America, and Asia in 2019

Abstract

Background. Aztreonam (ATM) is a monobactam stable to hydrolysis by metallo-β-lactamases (MBL). Avibactam (AVI) is a non-β-lactam β-lactamase inhibitor that inhibits serine carbapenemases (CPEs), such as ESBLs, KPCs, AmpC, and some OXAs. ATM-AVI is under clinical development for treatment of serious infections caused by Gram-negative bacteria (GNB), including MBL-producers. Methods. 2,582 GNB (1,630 Enterobacterales [ENT] and 952 nonfermentative-GNB) were consecutively collected (1/patient) from 56 medical centers located in Western Europe (W-EU; 22 centers in 10 nations), Eastern Europe (E-EU; 12 centers in 9 nations), Latin America (LATAM; 10 centers 6 nations), and the Asia-Pacific region (APAC; 12 centers in 8 nations) in 2019 and susceptibility (S) tested against ATM-AVI and comparators at a central laboratory by reference broth microdilution methods. Results. Overall, 99.9% of ENT (MIC50/90, 0.06/0.25 mg/L), including 99.1% of carbapenem-resistant ENT (CRE; MIC50/90, 0.25/0.5 mg/L), were inhibited at an ATM-AVI MIC of ≤ 8 mg/L (Table). CRE rates were 1.4%, 23.7%, 6.3%, and 9.6% in W-EU, E-EU, LATAM, and APAC, respectively (6.9% overall). A CPE was identified in 95 of 113 CRE isolates (84.1%). These CPEs included NDM-like (31.0% of CRE), KPC-like (26.5%), OXA-48-like (24.8%), and VIM-like (7.1%). Six isolates produced 2 CPEs. The highest ATM-AVI MIC value among MBL-producers (n=43; MIC50/90, 0.12/0.5 mg/L) was 4 mg/L. Among P. aeruginosa, 75.1% were inhibited at ≤ 8 mg/L of ATM-AVI; S to meropenem (MEM), piperacillin-tazobactam, and ceftazidime were 69.4%, 72.5%, and 75.7%, respectively, and ranged from 64.3% in E-EU to 82.0% in W-EU. MEM non-S P. aeruginosa varied from 22.2% in W-EU to 54.8% in E-EU. ATM-AVI was highly active against S. maltophilia, inhibiting 95.0%, 100.0%, 100.0%, and 90.0% of isolates from W-EU, E-EU, LATAM, and APAC, respectively, at ≤8 mg/L. S. maltophilia S to cotrimoxazole were 90.0%, 97.7%, 85.7%, and 100.0% in W-EU, E-EU, LATAM, and APAC, respectively. ATM-AVI also was very active against Burkholderia spp. (highest MIC, 8 mg/L). Conclusion. Our results support clinical development of ATM-AVI to treat pneumonia caused by ENT (including MBL-producers), P. aeruginosa, S. maltophilia, and Burkholderia spp.