Aztreonam/avibactam Activity Against a Large Collection of Carbapenem-Resistant Enterobacterales (CRE) Collected in Hospitals from Europe, Asia and Latin America (2019-21)

Background Aztreonam/avibactam is under development to treat infections caused by Gram-negative bacteria. We evaluated the in vitro activities of aztreonam/avibactam and comparators against a global collection of carbapenem-resistant Enterobacterales (CRE), including ceftazidime/avibactam-resistant isolates. Methods Isolates were consecutively collected (24 924; 1/patient) from 69 medical centres in 36 countries during 2019-21. Isolates were susceptibility tested by CLSI broth microdilution. All CRE isolates (n = 1098; 4.4%) were in silico screened for carbapenemase (CPE) genes after genome sequencing. CRE susceptibility results were stratified by CPE, geography and resistance phenotype. Results Aztreonam/avibactam inhibited 99.6% of CREs at <= 8 mg/L (MIC50/90, 0.25/0.5 mg/L), including 98.9% (345/349) of ceftazidime/avibactam-resistant isolates. Aztreonam/avibactam activity was consistent across geographical regions (98.9%-100.0% inhibited at <= 8 mg/L), but susceptibility to comparators varied markedly. Susceptibility (CLSI criteria) for ceftazidime/avibactam and meropenem/vaborbactam ranged from 80.2% and 77.5% in Western Europe to 39.5% and 40.3% in the Asia-Pacific region, respectively. Aztreonam/avibactam retained activity against isolates non-susceptible to colistin (99.7% inhibited at <= 8 mg/L) or tigecycline (98.6% inhibited at <= 8 mg/L). A CPE gene was identified in 972 CRE isolates (88.5%). The most common CPEs were KPC (43.1% of CREs), NDM (26.6%) and OXA-48-like (18.7%); 57 isolates (5.2%) had >1 CPE gene. Aztreonam/avibactam inhibited 99.9% of CPE producers at <= 8 mg/L, whereas ceftazidime/avibactam and meropenem/vaborbactam exhibited limited activity against isolates producing MBL and/or OXA-48-like enzymes. Conclusions Aztreonam/avibactam activity was not adversely affected by clinically relevant CPEs. Our results support aztreonam/avibactam development to treat infections caused by CRE, including MBL producers.