In vitro activities of ceftazidime–avibactam, ceftolozane–tazobactam, meropenem–vaborbactam and other comparators against Pseudomonas aeruginosa isolates with discrepant resistance to carbapenems: Data from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program, 2012–2021

Objectives: This study aimed to investigate the in vitro susceptibility and β-lactamase-encoding genes of Pseudomonas aeruginosa (P. aeruginosa) isolates with discrepant resistance to various carbapenems. Methods: Data on P. aeruginosa isolates were obtained from the Antimicrobial Testing Leadership and Surveillance program from 2012–2021. Minimum inhibitory concentrations of P. aeruginosa isolates were determined using the broth microdilution method. β-lactamase-encoding genes were identified using multiplex polymerase chain reaction assays. Results: Among the P. aeruginosa isolates that were tested, the percentages of isolates resistant to imipenem, meropenem and doripenem were 26.9% (14 447 of 53 617), 20.5% (14 098 of 68 897) and 17.5% (3660 of 20 946), respectively. Imipenem-resistant P. aeruginosa isolates were more susceptible to all tested antimicrobial agents (except colistin) than the meropenem-resistant or doripenem-resistant P. aeruginosa isolates. Carbapenemase genes were detected in 14.3% (2020 of 14 098) of meropenem-resistant P. aeruginosa isolates. Imipenem-resistant meropenem-susceptible P. aeruginosa isolates had higher susceptibility profiles, fewer carbapenemase genes (0.3% [five of 1858] vs. 4.1% [10 of 242]; P < 0.05) and a lower risk of being classified as multidrug-resistant than the imipenem-susceptible meropenem-resistant isolates (16.1% [299 of 1858] vs. 73.6% [178 of 242]; P < 0.05). Among all β-lactam combination agents, ceftazidime–avibactam and ceftolozane–tazobactam had higher susceptibility rates than meropenem–vaborbactam for meropenem-resistant P. aeruginosa (61.8% and 55.5% vs. 30.2%; P < 0.05). Conclusion: Discrepancy in the resistance of different P. aeruginosa isolates to various carbapenems suggests their different underlying resistance mechanisms. These findings can be useful for effective resistance trend monitoring and accurate antimicrobial treatment in the future.