Quesada-Gomez C
Universidad de Costa Rica, Costa Rica
Title: Recombination in the substrate recognition domain of TcdB confers a variant glucosyl transferase activity and a distinctive cytopathic effect to a Clostridium difficile strain from the hypervirulent clade II
Biography
Biography: Quesada-Gomez C
Abstract
Clostridium difficile NAP1 strains are responsible for nosocomial outbreaks worldwide. The increased pathogenic potential of these strains has been attributed to over production of toxins and fluoroquinolone resistance. During a C. difficile nosocomial outbreak in Costa Rica, a strain was found to induce a distinct cytopathic effect (CPE) different from the canonical arborizing CPE. The strain was further identified as a NAP1 isolate (NAP1V) of the hypervirulent clade II that harbored a silent mutation in the gyrA gene. After toxin purification, cells treated with TcdB of the NAP1V strain (TcdBV), displayed a rounded and surface detached phenotype resembling that induced by C. difficile TcdB toxin A-negative strains. The effect mediated by the TcdBV was due to differences in substrate preferences that resulted in different glucosylation patterns of the various GTPases. Whereas TcdB from classical NAP1/027 strains glucosylated RhoA, Rac and Cdc42, TcdBV did not used RhoA as substrate and displayed less affinity for Cdc42. Sequence comparison of the functional domains of TcdBv with other C. difficile strains along with comparative genomic analysis revealed that TcdBv is a NAP1 toxin but with modifications within the enzymatic domain. The enzymatic domain is identical to that of a NAP9/017 strains (A-B+). We also provide evidence that the NAP1 strains glucosylate a broader spectrum of GTPases in vitro as both toxins glucosylated Rap and R-Ras. These findings provide insight into the role of the glucosyl tranferase activity in the pathogenesis of C. difficile variant TcdB strains and the hyper virulent NAP1 strains.