Objective: Limited treatment options exist for infections caused by carbapenem-resistant Gram-negative bacilli, with polymyxins and ceftazidime-avibactam being the last line of defense. This study aims to assess the in vitro effectiveness of ceftazidime-avibactam susceptibility in Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa strains isolated from various clinical samples in intensive care units of our hospital.

Methods: During the period between April 2022 and March 2024, a total of 367 isolates were included in the study. These isolates consisted of 65 E. coli, 217 K. pneumoniae, and 85 P. aeruginosa, which were identified as the causative agents in various clinical samples of intensive care unit patients. Isolates were identified using MALDI-ToF/MS (matrix-assisted laser desorption ionization-time of flight mass spectrometry). Carbapenem resistance and CZA susceptibility were assessed using disk diffusion. Results were interpreted according to EUCASTv.14.0.

Results: The susceptibility rates of CZA in carbapenem-susceptible E. coli, K. pneumoniae, and P. aeruginosa strains were 100%, 97.7%, and 97.3%, respectively. The susceptibility rates of CZA in carbapenem-resistant E. coli, K. pneumoniae, and P. aeruginosa strains were 68.4%, 64.1%, and 79.2%, respectively. It is worrying that K. pneumoniae is the most frequently detected agent in our hospital’s intensive care units and its CZA susceptibility is lower than E. coli and P. aeruginosa strains.

Conclusion: In this study, it is worrying that the CZA susceptibility rate in K. pneumoniae strains was found to be lower than in E. coli and P. aeruginosa strains. Meticulous implementation of appropriate antibiotic use policies will allow the control of antibiotic resistance.