Effector genes of type III secretion system and biofilm formation in virulent Pseudomonas aeruginosa isolates carrying bla KPC-2 and bla PDC-5 genes in hospital environment

<b>Introduction.</b> In critically ill patients, the occurrence of multidrug-resistant <i>Pseudomonas aeruginosa</i> infection is a significant concern, given its ability to acquire multidrug-resistant, form biofilms and secrete toxic effectors.<b>Hypothesis or Gap Statement.</b> In Brazil, limited data are available regarding the prevalence of dissemination, and the impact of the type III secretion system (T3SS) on toxin production and biofilm formation in clinical isolates of <i>P. aeruginosa</i>.<b>Aim.</b> This study investigates the dissemination of virulent <i>P. aeruginosa</i> harbouring the <i>bla</i> _KPC-2 and <i>bla</i> _PDC-5 genes, the presence of T3SS genes and their biofilm-forming capability.<b>Methodology.</b> A total of 128 non-duplicate clinical isolates of carbapenem-resistant <i>P. aeruginosa</i> (CRPA) from different sources collected from eight hospitals were examined. Detection was performed by PCR of the T3SS genes (<i>exo</i>U, <i>exo</i>T, <i>exo</i>S and <i>exo</i>Y), carbapenemases (<i>bla</i> _KPC, <i>bla</i> _GIM and <i>bla</i> _NDM) and beta-lactamase gene (<i>bla</i> _PDC). PFGE and phenotypic biofilm production (initial adhesion assay and biofilm cell concentration) were performed.<b>Results.</b> We found <i>exo</i>T⁺ (86%) to be the most frequent genotypic variant, followed by <i>exo</i>Y⁺ (61%). Notably, a substantial proportion of isolates exhibited the simultaneous presence of <i>exo</i>U⁺ and <i>exo</i>S⁺ genes, along with a high prevalence of <i>bla</i> _KPC-2 ⁺ (64%) and <i>bla</i> _PDC-5 ⁺ (64%) among the disseminated clones in the evaluated region. Additionally, 78% of the isolates demonstrated biofilm-forming capability, and two distinct clonal profiles were identified and disseminated both intra- and inter-hospital. Also, it was revealed that the <i>exo</i>U genotype was significantly more frequent among multidrug-resistant strains.<b>Conclusion.</b> These findings underscore the ability of multiple virulent and biofilm-producing clones of CRPA to propagate effectively.