Analysis of resistance characteristics to ceftazidime/avibactam and carbapenemase gene distribution in carbapenem-resistant Pseudomonas aeruginosa in Ningbo

OBJECTIVE To analyze the current status of resistance to ceftazidime/avibactam (CZA), clinically relevant characteristics and carbapenem-resistant gene distribution in carbapenem-resistant Pseudomonas aeruginosa (CRPA) in Ningbo, providing a basis for the prevention, control and treatment of CRPA infections in this region. METHODS A total of 279 non-repetitive CRPA strains, initially isolated clinically from Jan. 2022 to Oct. 2024 at the First Affiliated Hospital of Ningbo University, were collected. The susceptibility of CRPA to CZA was determined by the disk diffusion method. Based on the results, the strains were divided into a CZA-resistant group (n=68) and a CZA-sensitive group (n=211). Clinical data of patients from whom the strains were isolated were analyzed, and carbapenemase genes in CRPA strains were detected by polymerase chain reaction (PCR) amplification technology. RESULTS The resistance rate of CRPA to CZA was 24.37%. The strains in the CZA-resistant group were mainly sourced from respiratory secretions (51 strains, 75.00%), and were predominantly distributed in the intensive care unit (30 strains, 44.12%). Patients in the CZA-resistant group had a higher proportion of recent injury history, skin and soft tissue infection history, invasive procedures (indwelling drainage tubes, central venous catheterization) and antibacterial drug exposure (P＜ 0.05). The drug susceptibility results showed that the resistance rates of the CZA-resistant group to ceftazidime, aztreonam, meropenem, tobramycin, amikacin, ciprofloxacin, piperacillin/tazobactam and cefoperazone/sulbactam were all higher than those of the CZA-sensitive group (P＜ 0.05), and its multidrug-resistant (MDR) rate was as high as 94.12%, higher than that of the CZA-sensitive group (P＜ 0.05). The detection rate of the bla_NDM gene in the CZA-resistant group (7.35%) was higher than that in the CZA-sensitive group (P＜ 0.05). CONCLUSIONS The resistance rate of CRPA to CZA in Ningbo is relatively high, closely associated with invasive procedures and antibacterial drug exposure. CZA-resistant strains often exhibit an MDR phenotype, and bla_NDM may be a key resistance mechanism.