Susceptibility of gram-negative isolates collected in Taiwan to imipenem/relebactam and comparator agents- SMART 2018-2021

Background: Imipenem/relebactam (IMR) was approved for patient use in Taiwan in 2023. We evaluated the in vitro susceptibility of recent Gram -negative pathogens collected in Taiwan hospitals to IMR and comparators with a focus on carbapenem-resistant and KPC-carrying non-Morganellaceae Enterobacterales (NME), and carbapenem-resistant Pseudomonas aeruginosa (CRPA). Methods: From 2018 to 2021, eight hospitals in Taiwan each collected up to 250 consecutive, aerobic or facultative, Gram -negative pathogens per year from patients with bloodstream, intraabdominal, lower respiratory tract, and urinary tract infections. MICs were determined using Clinical Laboratory Standards Institute (CLSI) broth microdilution. Most isolates that were IMR-, imipenem-, or ceftolozane/tazobactam-nonsusceptible were screened for B-lactamase genes by PCR or whole-genome sequencing. Results: Ninety-eight percent of NME (n = 5063) and 94% of P. aeruginosa (n = 1518) isolates were IMR-susceptible. Percent susceptible values for non-carbapenem B-lactam comparators, including piperacillin/tazobactam, were 68-79% for NME isolates, while percent susceptible values for all B-lactam comparators, including meropenem, were 73-81% for P. aeruginosa. IMR retained activity against 93% of multidrug-resistant (MDR) NME and 70% of MDR P. aeruginosa. Sixty-five percent of carbapenem-resistant NME and 81% of KPC-positive NME (n = 80) were IMR-susceptible. IMR inhibited 70% of CRPA (n = 287). Fifty percent of IMRnonsusceptible NME tested for B-lactamase carriage had an MBL or OXA-48-like enzyme, whereas most (95%) IMR-nonsusceptible P. aeruginosa examined did not carry acquired B-lactamase genes. Conclusion: Based on our in vitro data, IMR may be a useful option for the treatment of hos- pitalized patients in Taiwan with infections caused by common Gram-negative pathogens, including carbapenem-resistant NME, KPC-positive NME, and CRPA. Copyright 2023, Formosan Medical Association. Published by Elsevier Taiwan LLC. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/).