Journal of Bacteriology & Parasitology

Recombination in the substrate recognition domain of TcdB confers a variant glucosyltransferase activity and a distinctive cytopathic effect to a Clostridium difficile strain from the hypervirulent clade II

3^rd International Congress on Bacteriology and Infectious Diseases

August 04-06, 2015 Valencia, Spain

Quesada-Gomez C1, Lopez-Urena D1, Castro C2, Kroh H2, Chumbler N2, Orozco-Aguilar J1, Guzman-Verri C3, Moreno E3, Rodriguez C1, Lawley T4, Lacy B2 and Chaves-Olarte E1

Posters-Accepted Abstracts: J Bacteriol Parasitol

Abstract:

Clostridium difficile NAP1 strains are responsible for nosocomial outbreaks worldwide. The increased pathogenic potential
of these strains has been attributed to overproduction 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 glucosylatedRhoA, Rac and Cdc42, TcdBV did not used
RhoA as substrate and displayed less affinity for Cdc42. Sequence comparison of the functional domains of TcdBvwith 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 glucosyltranferase activity in the pathogenesis of C. difficile variant TcdB strains and the
hypervirulent NAP1 strains.

Biography :

Carlos Quesada-Gómez is a lecturer on Anaerobic Bacteriology, School of Microbiology, University of Costa Rica. He has a M.Sc. in Medical Bacteriology and
is currently a PhD. Candidate working with Clostridium difficile. His research group is working on the molecular characterization of different isolates by PFGE,
toxinotyping, MLST and whole genome sequence methods which have made possible the description of the hipervirulent NAP1/027 and other novel genotypes in
Costa Rica and Latin America. C. difficile pathogenesis is another area of study in which the level of virulence is being associated with the genotypes and its toxins
using cellular and animal models.