Investigation of ceftazidime-avibactam susceptibility in clinical isolates of gram-negative bacteria.

Background: Our study investigated the susceptibility rate of ceftazidime-avibactam and the risk factors associated with its resistance by analyzing gram-negative bacteria isolated from various patient samples.

Methods: Between March and November 2020, 1119 gram-negative bacteria strains were isolated from patient samples in Acıbadem Healthcare Group hospitals; ceftazidime-avibactam susceptibility results were evaluated using a 10/4µg (Oxoid, UK) disc and evaluated according to Eucast 2020 recommendations. Patient and isolate characteristics that could be risk factors were retrospectively investigated and statistically analyzed using SPSS 25.0.

Results: Male patients made up 52% (n = 581) of the study's total patient population, and they averaged 55.5 ± 24.9 years old. Of 1119 gram-negative strains culture and antibiogram, 1023 (91.4%) were sensitive to ceftazidime-avibactam. An increased risk of resistance was observed with female gender (OR = 2.29; CI 95% [1.45-3.61]; p < 0.05), Pseudomonas aeruginosa (OR = 1.67, CI 95% [1.03-2.7]; p < 0.05), the presence of multidrug-resistance (MDR) (OR = 4.07, CI 95% [2.47-6.7]; p < 0.05) pandrug-resistance (PDR) (OR = 12, (CI) 95% [9.9-14.7] ]; p < 0.05) and admission to intensive care unit (ICU) (OR = 1.89, CI 95% [1.22-2.93]; p < 0.05).

Discussion: The resistance rate of ceftazidime-avibactam was found to be 8.6%, and it was thought that resistant strains produced metallo-ß-lactamase (MBL) type carbapenemase. Risk factors were female gender, Pseudomonas aeruginosa, MDR, PDR, and admission to ICU. Therefore, studying the ceftazidime-avibactam susceptibility test together with gram-negative bacteria identification, especially in groups at risk for resistance, is one of the important factors that can positively affect the success of treatment.