Comparison of in vitro susceptibility methods against ceftazidime avibactam in carbapenem-resistant pseudomonas aeruginosa strains and investigation of some carbapenemase genes

Objective: Alternative methods are needed to ceftazidime avibactam sensitivity detect reliably. In this study, it was aimed to compare the reference method broth microdilution and disk diffusion methods to evaluate ceftazidime avibactam susceptibility in carbapenem resistant Pseudomonas aeruginosa and to investigate the common carbapenemas genes (KPC, IMP, VIM, NDM, OXA-48, GES) using the polymerase chain reaction method. Materials and Methods: Between March 2021 and January 2023, 103 carbapenem resistant P. aeruginosa isolates isolated from clinical samples sent to Hitit University Çorum Erol Olçok Education and Research Hospital Medical Microbiology laboratory were included in the study. Disc diffusion and broth microdilution methods were used to determine ceftazidime avibactam susceptibility. Carbapenem inactivation method was used for the phenotypic determination of carbapenemase production. After DNA isolation for genotyping determination, polymerase chain reaction method was applied, the amplified gene regions were move by agarose gel electrophoresis and viewed under UV light. Results: According to the broth microdilution results of the isolates, 69% were found to be susceptible to ceftazidime avibactam, and 31% were found to be resistant to ceftazidime avibactam. 98 isolates to which the disk diffusion method was applied gave results compatible with broth microdilution results, two isolates were found within the area of technical uncertainty, and three isolates were observed discordant results.