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.

Introduction. In critically ill patients, the occurrence of multidrug-resistant Pseudomonas aeruginosa infection is a significant concern, given its ability to acquire multidrug-resistant, form biofilms and secrete toxic effectors.Hypothesis or Gap Statement. 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 P. aeruginosa.Aim. This study investigates the dissemination of virulent P. aeruginosa harbouring the bla _KPC-2 and bla _PDC-5 genes, the presence of T3SS genes and their biofilm-forming capability.Methodology. A total of 128 non-duplicate clinical isolates of carbapenem-resistant P. aeruginosa (CRPA) from different sources collected from eight hospitals were examined. Detection was performed by PCR of the T3SS genes (exoU, exoT, exoS and exoY), carbapenemases (bla _KPC, bla _GIM and bla _NDM) and beta-lactamase gene (bla _PDC). PFGE and phenotypic biofilm production (initial adhesion assay and biofilm cell concentration) were performed.Results. We found exoT⁺ (86%) to be the most frequent genotypic variant, followed by exoY⁺ (61%). Notably, a substantial proportion of isolates exhibited the simultaneous presence of exoU⁺ and exoS⁺ genes, along with a high prevalence of bla _KPC-2 ⁺ (64%) and bla _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 exoU genotype was significantly more frequent among multidrug-resistant strains.Conclusion. These findings underscore the ability of multiple virulent and biofilm-producing clones of CRPA to propagate effectively.