Mediterranean Journal of Infection, Microbes and Antimicrobials (Oct 2023)
Resistance Genes and Molecular Epidemiology in Ceftazidime-Avibactam-Resistant Pseudomonas aeruginosa Isolates
Abstract
Introduction: Increasing ceftazidime-avibactam (CZA) resistance in P. aeruginosa isolates is of serious concern worldwide. Therefore, studies on the underlying resistance mechanisms gain even more importance. The aim of this study was to investigate the presence of beta-lactamase genes reported to be associated with resistance, including metallo-beta-lactamases (MBL), in CZA-resistant P. aeruginosa strains and the clonal relationship between isolates. Materials and Methods: Ceftazidime-avibactam resistant P. aeruginosa strains isolated from various clinical specimens between December 2021 and March 2023 were included in this study. MALDI-TOF (VITEK-MS, bioMérieux, France) was used for the identification of strains. Ceftazidime-avibactam susceptibility was determined by disc diffusion method and resistant strains were also studied by gradient diffusion method (MIC strip, Liofilchem, Italy). Antibiotic susceptibility results were evaluated according to the European Committee for Antibiotic Susceptibility Testing criteria. blaKPC, blaNDM, blaIMP, blaVIM, blaOXA-48, blaOXA-2, blaOXA-10, blaGES, blaPER, blaVEB genes were determined using polimerase chain reaction, and clonal relationship was investigated by pulsed field gel electrophoresis. Results: A total of 38 CZA resistant P. aeruginosa strains were analyzed. The MIC50 and MIC90 values determined by the gradient diffusion method for CZA were ≥256 mg/l and ≥256 mg/l, respectively; the MIC range was found to be 32-256 mg/l. Among of 38 isolates, 11 (28.9%) isolates including 10 blaVIM (26.3%) and one blaIMP (2.6%) were positive for the MBL genes. The blaOXA-10 gene was found to be co-positive in seven of the blaVIM positive isolates and in one blaIMP positive isolate. In addition, blaOXA-10 alone was found in nine (23.6%) of the isolates, blaPER in two (5.2%) and blaGES in one (2.6%). No genes were found in 15 (39.4%) isolates. A total of 15 different genotypes consisting of eight different clusters were identified. Conclusion: It was determined that MBL production, especially blaVIM, was the most common cause of CZA resistance. blaOXA-10, blaPER and blaGES positivity were also found remarkable. Regarding molecular epidemiology, it was observed that the strains isolated predominantly from ICU patients had different genotypes and exhibited a polyclonal diversity.
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