Dissemination of Metallo--Lactamase-Producing Pseudomonas aeruginosa in Serbian Hospital Settings: Expansion of ST235 and ST654 Clones

This nationwide study aimed to investigate the molecular characteristics of metallo-beta-lactamase (MBL)-producing Pseudomonas aeruginosa in Serbia, underlying resistance mechanisms, the genetic context of detected MBL genes, and the clonal relationship between isolates harboring genes-encoding MBL. Overall, 320/5334 isolates collected from 2018 to 2021 were identified as P. aeruginosa. Carbapenem-resistant P. aeruginosa (CRPA) were screened for the presence of bla(VIM), bla(IMP), and bla(NDM), genes whereas MBL-positive isolates were tested for the presence of the bla(CTX-M-2), bla(PER), bla(TEM), bla(SHV), bla(VEB), and bla(GES). Multilocus sequence typing and phylogenomic analysis were performed for P. aeruginosa-producing MBL. The majority of the P. aeruginosa isolates were recovered from the lower respiratory tract (n = 120; 37.5%) and wound specimens (n = 108; 33.75%). CRPA isolates accounted for 43.1% (n = 138) of the tested isolates, 31 out of them being bla(NDM-1)-positive (22.5%). The colistin resistance rate was 0.3%. MLST analysis 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/bla(NDM-1), ST235/bla(NDM-1)/bla(PER-1), ST654/bla(NDM-1), ST654/bla(NDM-1)/bla(PER-1), and ST654/bla(NDM-1)/bla(GES-5). High-risk clones ST235 and ST654 identified for the first time in Serbia, are important vectors of acquired MBL and ESBL and their associated multidrug resistance phenotypes represent a cause for considerable concern.