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 (MIC(50/90), 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.