Activity of ceftolozane/tazobactam and imipenem/relebactam against clinical isolates of Enterobacterales and Pseudomonas aeruginosa collected in central and northern Europe (Belgium, Norway, Sweden, Switzerland)—SMART 2017–21

Abstract

Abstract Objectives To evaluate the in vitro activities of ceftolozane/tazobactam and imipenem/relebactam against clinical isolates of Gram-negative bacilli collected in four central and northern European countries (Belgium, Norway, Sweden, Switzerland) during 2017–21. Methods Participating clinical laboratories each collected up to 250 consecutive Gram-negative isolates per year from patients with bloodstream, intraabdominal, lower respiratory tract or urinary tract infections. MICs were determined by CLSI broth microdilution and interpreted using 2022 EUCAST breakpoints. β-Lactamase genes were identified in select β-lactam-non-susceptible isolate subsets. Results Ninety-five percent of all Enterobacterales (n = 4158), 95% of ESBL-positive non-carbapenem-resistant Enterobacterales (non-CRE) phenotype Escherichia coli and 85% of ESBL-positive non-CRE phenotype Klebsiella pneumoniae were ceftolozane/tazobactam susceptible. By country, 88% (Belgium), 91% (Sweden, Switzerland) and 96% (Norway) of ESBL-positive non-CRE phenotype Enterobacterales were ceftolozane/tazobactam susceptible. Greater than ninety-nine percent of non-Morganellaceae Enterobacterales and all ESBL-positive non-CRE phenotype Enterobacterales were imipenem/relebactam susceptible. Ceftolozane/tazobactam (96%) and imipenem/relebactam (95%) inhibited most Pseudomonas aeruginosa (n = 823). Both agents retained activity against ≥75% of cefepime-resistant, ceftazidime-resistant and piperacillin/tazobactam-resistant isolates; 56% and 43% of meropenem-resistant isolates were ceftolozane/tazobactam susceptible and imipenem/relebactam susceptible, respectively. By country, 94% (Belgium), 95% (Sweden) and 100% (Norway, Switzerland) of P. aeruginosa were ceftolozane/tazobactam susceptible and 93% (Sweden) to 98% (Norway, Switzerland) were imipenem/relebactam susceptible. Carbapenemase gene carriage among Enterobacterales and P. aeruginosa isolates was generally low (<1%) or completely absent with one exception: an estimated 2.7% of P. aeruginosa isolates from Belgium carried an MBL. Conclusions Recent clinical isolates of Enterobacterales and P. aeruginosa collected in four central and northern European countries were highly susceptible (≥95%) to ceftolozane/tazobactam and imipenem/relebactam.