Effector genes of type III secretion system and biofilm formation in virulent isolates carrying and genes in hospital environment.

In critically ill patients, the occurrence of multidrug-resistant infection is a significant concern, given its ability to acquire multidrug-resistant, form biofilms and secrete toxic effectors. 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 . This study investigates the dissemination of virulent harbouring the and genes, the presence of T3SS genes and their biofilm-forming capability. A total of 128 non-duplicate clinical isolates of carbapenem-resistant (CRPA) from different sources collected from eight hospitals were examined. Detection was performed by PCR of the T3SS genes (U, T, S and Y), carbapenemases ( , and ) and beta-lactamase gene ( ). PFGE and phenotypic biofilm production (initial adhesion assay and biofilm cell concentration) were performed. We found T (86%) to be the most frequent genotypic variant, followed by Y (61%). Notably, a substantial proportion of isolates exhibited the simultaneous presence of U and S genes, along with a high prevalence of (64%) and (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 U genotype was significantly more frequent among multidrug-resistant strains. These findings underscore the ability of multiple virulent and biofilm-producing clones of CRPA to propagate effectively.