Caracterização molecular de isolados clínicos de enterobacter spp. produtores de carbapenemases: determinantes de resistência aos carbapanêmicos e virulência, perfil plasmidial e tipagem molecular

Abstract

The genus Enterobacter spp. is one of the most important among Enterobacteriaceae family causing nosocomial infection in several clinical site, since its intrinsic and acquired resistance, the treatment is a challenge. It is growing the cases of carbapenem-resistant Enterobacter spp., through the action of enzymes called carbapenemases, associated with mobile genetic elements and disseminated by plasmids. Beyond the impact of antibiotic resistance in global health, Enterobacter spp. isolates can still present virulence factors, favoring the infectious process. Objectives: The aims of this study were to access the diversity of resistance genes responsible for production of carbapenemases and virulence genes; characterize carbapenemase-carriyng plasmids and determine the profile of genetic similarity among Enterobacter spp. isolated from patients admitted at Hospital de Base of São José do Rio Preto, SP. Material and Methods: DNA was extracted, carbapenem resistance genes and virulence genes were investigated, plasmids carbapenemase-carrying was characterized in terms of incompatibility group and size and molecular typing by PFGE-XbaI. Results: The blaKPC-2 gene was the determinant of resistance to carbapenems in 56 (98.2%) isolates of E. cloacae complex and 11 (100%) E. aerogenes and blaNDM-1 in one (1.8%) isolate of E. cloacae complex. Among virulence genes detected in isolates of the E. cloacae complex, entB was detected in 92.9%, iroN (40.3%), irp2 (7%) and mrkD (6.9%). In E. aerogenes isolates, entB (100%), irp2 (72.7%), iroN (54.5%) and fimH (27.7%) were detected. The size of the plasmids carrying the blaKPC-2 genes was estimated in 96.5% of the isolates of the E. cloacae complex and 100% of the E. aerogenes, ranging in size from 15 to 210 Kb, with 60 to 70 Kb being the common sizes. NDM carbapenemase is carried by an approximately 150 Kb plasmid. The incompatibility group of the blaKPC-2 carrier plasmids was determined in 84% of the E. cloacae complex isolates and 100% of the E. aerogenes, the Inc identified were IncN, IncN2, IncM and IncA/C. Molecular typing revealed a wide diversity of pulsotypes between isolates of the E. cloacae complex (46 clusters and generated 8 clusters called A, B, C, D, E, F, G and H with more than one isolate) and E. aerogenes (9 clusters, one being formed by more than one isolate). Conclusion: The analyzes showed that the blaKPC-2 gene is the main responsible for the resistance to carbapenems among isolates studied. Genes associated with iron capture are the main determinants of virulence; IncM and IncN plasmids are the main carriers of the blaKPC-2 gene. Genetically unrelated isolates are associated with infections in the patients studied, but the identification of clusters highlights the occurrence of cross-transmission.