Potencial de virulência de amostras de Corynebacterium spp. isoladas de pacientes hospitalizados

Abstract

In the last decades, non-diphtheritic corynebacteria have emerged as true pathogens of nosocomial infections and the pattern of resistance of these microorganisms to multiple drugs has been emphasized. However, the virulence mechanisms of these pathogens are not well understood. In this perspective, the present work aimed to investigate the virulence potential of Corynebacterium spp. isolated from human clinical material and to characterize the genetic determinants involved with a Metallo-Beta-Lactamase (MBL) phenotype in our bacterial strains. In this study, clinical strains of Corynebacteirum amycolatum (3 strains), Corynebacterium accolens (4 strains), Corynebacterium minutissimum (1 strain) and Corynebacterium falsenii (1 strain) were studied. Assays of adherence and invasion to the U-397 macrophage lineage were performed at 3 and 6 hours. The nematode Caenorhabditis elegans was used as an in vivo model for the virulence assay. Corynebacterium spp. phenotypically producing MBL were submitted to the polymerase chain reaction technique to identify the genetic determinant responsible for bacterial resistance. All samples showed adherence to the macrophage lineage U-937. All strains of Corynebacterium spp. caused a decline in the survival curve of C. elegans, when compared to the survival curve of nematodes exposed to the control strain. Regarding the morphology and development of the nematodes infected by Corynebacterium spp., 100.0% of the strains caused deformation of the anal region (Dar phenotype) and abdominal distension. The “worm bagging” phenotype was observed for all strains tested. The bla gene, which encodes a class A beta-lactamase, was detected in multidrug-resistant strains of C. amycolatum. In conclusion, the study highlights the relevance of Corynebacterium spp. as a multidrug-resistant nosocomial pathogen. To the best of our knowledge, this is the first identification of imipenem-resistant C. amycolatum, showing the production of MBL and positive for bla gene. Finally, the bla gene was sequenced and the result deposited in GenBank. Furthermore, the results showed interaction between the nematode and Corynebacterium spp. resulted in morphological changes that may provide insights into aspects of bacterial pathogenicity and mechanisms underlying physiological processes in humans. Thus, it is suggested that medical surveillance programs include control strategies to reduce potential risk factors for nosocomial infections by Corynebacterium spp