LAUSR

We examined the in vitro susceptibility of meropenem-nonsusceptible Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex isolates from five consecutive annual SIDERO-WT surveillance studies (2014-2019) to cefiderocol and comparator agents in the context of their carbapenemase carriage. 1,003 Enterobacterales, 1,758 P. aeruginosa, and 2,809 A. baumannii complex isolates from North America and Europe that were meropenem nonsusceptible (CLSI M100, 2022) were molecularly characterized for β-lactamase content by PCR followed by Sanger sequencing or by whole genome sequencing. Among Enterobacterales, 91.5% of metallo-β-lactamase (MBL)-producing, 98.4% of KPC-producing, 97.3% of OXA-48 group-producing, and 98.7% of carbapenemase-negative, meropenem-nonsusceptible isolates were cefiderocol susceptible (MIC ≤4 mg/L). Among P. aeruginosa, 100% of MBL-producing, 100% of GES carbapenemase-producing, and 99.8% of carbapenemase-negative, meropenem-nonsusceptible isolates were cefiderocol susceptible (MIC ≤4 mg/L). Among A. baumannii complex, 60.0% of MBL-producing, 95.6% of OXA-23 group-producing, 89.5% of OXA-24 group-producing, 100% of OXA-58 group-producing, and 95.5% of carbapenemase-negative, meropenem-nonsusceptible isolates were cefiderocol susceptible (MIC ≤4 mg/L). Cefiderocol was inactive against A. baumannii complex isolates carrying a PER or VEB β-lactamase (n = 103; 15.5% susceptible). Ceftazidime-avibactam and ceftolozane-tazobactam were inactive against MBL-carrying and A. baumannii complex isolates; ceftolozane-tazobactam was also inactive against serine carbapenemase-carrying Enterobacterales and P. aeruginosa. In summary, cefiderocol was highly active in vitro against Gram-negative isolates carrying MBLs and serine carbapenemases, as well as carbapenemase-negative, meropenem-nonsusceptible isolates.