Prevalence of cytolethal distending toxin production in Campylobacter jejuni and relatedness of Campylobacter sp. cdtB gene

Abstract

Campylobacter jejuni produces a toxin called cytolethal distending toxin (CDT). The genes encoding this toxin in C. jejuni 81-176 were cloned and sequenced. The nucleotide sequence of the genes revealed that there are three genes, cdtA, cdtB, and cdtC, encoding proteins with predicted sizes of 30,116, 28,989, and 21,157 Da, respectively. All three proteins were found to be related to the Escherichia coli CDT proteins, yet the amino acid sequences have diverged significantly. All three genes were required for toxic activity in a HeLa cell assay. HeLa cell assays of a variety of C. jejuni and C. coli strains suggested that most C. jejuni strains produce significantly higher CDT titers than do C. coli strains. Southern hybridization experiments demonstrated that the cdtB gene is present on a 6.0-kb ClaI fragment in all but one of the C. jejuni strains tested; the cdtB gene was on a 6.9-kb ClaI fragment in one strain. The C. jejuni 81-176 cdtB probe hybridized weakly to DNAs from C. coli strains. The C. jejuni 81-176 cdtB probe did not hybridize to DNAs from representative C. fetus, C. lari, C. "upsaliensis," and C. hyointestinalis strains, although the HeLa cell assay indicated that these strains make CDT. PCR experiments indicated the probable presence of cdtB sequences in all of these Campylobacter species. Campylobacter jejuni is established as one of the most frequent bacterial causes of diarrheal disease in humans throughout the world (6, 20, 33). The disease can be variable, but patients typically have watery diarrhea that often contains mucus and may progress to bloody diarrhea (5, 6). Whether specific disease symptoms correlate with specific virulence factors or pathogenic traits is not known. C. jejuni has been reported to produce toxins, although definitive reports of these toxins have not appeared, and it is not clear how many different toxins C. jejuni actually produces (11, 16, 18, 21, 23, 28). Consequently, the role of any toxin in pathogenesis has not been established. Cytolethal distending toxin (CDT) production by C. jejuni was first described by Johnson and Lior (16) in 1988. CDT activity in culture supernatants caused several cultured cell lines, including HeLa and Vero cells, to become slowly distended over a 2-to 4-day period, after which the cells disintegrated. The activity was heat sensitive, trypsin sensitive, and nondialyzable (16). Johnson and Lior screened over 500 C. jejuni isolates obtained from many different countries and found that approximately 41% produced CDT. The CDT-positive isolates included representatives of all four C. jejuni biotypes and numerous serogroups. They also tested C. coli, C. lari, and C. fetus strains and showed that about 42% of these strains produced CDT (16). These Campylobacter species, as well as C. hyointestinalis and C. "upsaliensis," have all been shown to cause diarrheal disease in humans, although they apparently cause the disease much less frequently in the United States than C. jejuni does (8, 10, 26, 32, 33, 37). Johnson and Lior (13-15) also report...

The bile salt sodium taurocholate inducesCampylobacter jejuniouter membrane vesicle production and increases OMV-associated proteolytic activity

“…As with the other Proteobacteria pathogens Haemophilus ducreyi, Aggregatibacter actinomycetemcomitans and Shigella dysenteriae, C. jejuni possesses CDT that interferes with normal cell cycle progression, resulting in G 2 arrest (Pickett et al, 1996;Purdy et al, 2000;Whitehouse et al, 1998). CDT (encoded by the cdtABC operon) is the only identified toxin in C. jejuni, yet the role that host metabolites such as bile salts play in inducing CDT secretion is unclear.…”

The role of Campylobacter jejuni cytolethal distending toxin in gastroenteritis: toxin detection, antibody production, and clinical outcome

“…The toxin is a tripartite 'AB 2 ' holotoxin contains an A, B, and C subunit, encoded by three adjacent genes, cdtA, cdtB, and cdtC (8)(9)(10)(11). The CdtB protein is the active toxic subunit A, whereas CdtA and CdtC peptides comprise the B subunit responsible for CDT binding and delivery of CdtB into cells (8,11,12). Studies investigating the short-and long-term effects of campylobacteriosis (13)(14)(15)(16)(17), and the putative correlation between a host specific marker and clinical outcome have been reported (13,14), but none to our knowledge have looked at the correlation between clinical outcome and bacterial CDT production.…”

Cytolethal distending toxin of Actinobacillus actinomycetemcomitans

“…Two small open reading frames (ORFs) of unknown function reside upstream of the cdtA gene in A. actinomycetemcomitans strains. Cdt's have been reported in pathogenic strains of Escherichia coli, Shigella dysenteriae and Campylobacter jejuni (12)(13)(14). The cytolethal distending toxin (Cdt) of Actinobacillus actinomycetemcomitans, a periodontal pathogen, is a newly described cytotoxin with immunosuppressive properties, capable of causing cell cycle arrest of lymphocytes.…”