Submitted to: Rushmore Conference on Mechanisms in Pathogenesis of Enteric Diseases
Publication Type: Abstract Only
Publication Acceptance Date: 9/29/2005
Publication Date: 9/29/2005
Citation: Dassanayake, R.P., Stryker, C.J., Johnson, R.K., Muraoka, W.T., Wesley, I.V., Duhamel, G.E. 2005. Characterization of a novel Campylobacter cytolethal distending toxin from Campylobacter hyointestinalis subsp. hyointestinalis isolated from humans and pigs [abstract]. Rushmore Conference on Mechanisms in Pathogenesis of Enteric Diseases. p. 33.
Technical Abstract: Campylobacter hyointestinalis was first described in pigs with enteric disease over two decades ago, and since then it has been identified as an important cause of enteritis in human beings. A novel bacterial toxin, designated cytolethal distending toxin (CDT) was identified in the reference porcine C. hyointestinalis ATCC 35217 in 1996, however, the sequence of the gene encoding the toxin sub-unit, cdtB, as well as the level and prevalence of CDT activity among clinical isolates have not been investigated. The aim of the present study was to compare the sequence of C. hyointestinalis cdtB and CDT activity of four porcine and two human clinical isolates to reference Campylobacter strains. The identity of each isolate was confirmed on the basis of phenotypic and partial 23S rDNA gene sequence analysis. Comparative phylogenetic analysis of partial nucleotide and amino acid sequences of cdtB revealed that human and porcine C. hyointestinalis formed a cluster distinct from all known Campylobacter species. Light and confocal laser scanning microscopic examinations of HeLa and INT-407 cells incubated with whole-cell lysates of C. hyointestinalis showed characteristic cytoplasmic and nuclear enlargements indicative of CDT activity. Compared with HeLa and INT-407 cells incubated with control medium where respectively less than 9.1% and 11.5% of the cells were arrested in the G2/M phase of the cell cycle, quantitative flow cytometric analysis of cells incubated with C. hyointestinalis CDT had greater than 73.1% and 83.3% of the cells arrested. We conclude that C. hyointestinalis isolated from humans and pigs produce levels of CDT similar to C. jejuni, but have a cdtB gene that is distinct from other Campylobacter species. The C. hyointestinalis cdtB gene-specific PCR assay developed in this study might be of assistance for differentiating this species from other pathogenic Campylobacter species.