Dissemination of metallo-β-lactamase-producing Pseudomonas aeruginosa in Serbian hospital settings: expansion of ST235 and ST654 clones

Abstract Background: Pseudomonas aeruginosa is one of the most common nosocomial pathogens worldwide. Limited information on beta-lactamase-producing P. aeruginosa in Serbia is available. The aim of this nationwide study was to investigate the molecular characteristics of metallo-β-lactamase (MBL)-producing P. aeruginosa in Serbia, to characterize underlying resistance mechanisms, to analyze the genetic context of detected MBL genes and clonal relationship between isolates harboring genes encoding MBL. Methods: A total of 320 isolates of P. aeruginosa were identified out of 5334 bacterial isolates collected from 2018 to 2021. Carbapenem-resistant P. aeruginosa (CRPA) were screened for the presence of blaVIM, blaIMP, and blaNDM, genes whereas MBL-positive isolates were tested for the presence of the genes blaCTX-M-2, blaPER, blaTEM, blaSHV, blaVEB, and blaGES. Multilocus sequence typing and phylogenomic analysis were performed for P. aeruginosa producing MBL. Results: P. aeruginosa isolates were recovered from the lower respiratory tract (n=120; 37.5%), wound specimens (n=108; 33.75%), and urine samples (n=71; 22.2%), mainly from patients admitted to the intensive care unit (n=178; 55.6%). CRPA isolates accounted for 43.1% (n=138) of the tested P. aeruginosa and 31 out of these were blaNDM-1-positive (22.5%). Colistin was the most effective antibiotic, with a resistance rate of 0.3%. MLST analysis of all blaNDM-1-positive isolates (n=31) revealed the occurrence of ST235 (n=25) and ST654 (n=6), mostly confined to Serbia. The distribution of beta-lactamase encoding genes in these isolates suggested clonal dissemination and possible recombination: ST235/blaNDM-1, ST235/blaNDM-1/blaPER-1, ST654/blaNDM-1, ST654/blaNDM-1/blaPER-1, and ST654/blaNDM-1/blaGES-5. Conclusions: High-risk clones ST235 and ST654 identified for the first time in Serbia, are important vectors of acquired MBL and ESBL in Serbia and their associated multidrug resistance (MDR) phenotypes represent a cause for considerable concern.