Distribution of the cytolethal distending toxin A gene (cdtA) among species of Shigella and Vibrio, and cloning and sequencing of the cdt gene from Shigella dysenteriae.

We investigated the distribution of the cytolethal distending toxin A gene (cdtA) among S. dysenteriae, Vibrio cholerae 01 and Vibrio parahaemolyticus by polymerase chain reaction (PCR) using primers constructed from the nucleotide sequences of Escherichia coli cdtA gene reported independently by Scott and Kaper (Infect Immun 1994; 62: 244-51) and by Pickett et al. (Infect Immun 1994; 62: 1046-51). The cdtA gene reported by Scott and Kaper was found to occur among eight of the 35 strains of S. dysenteriae but was not found among V. cholerae O1 and V. parahaemolyticus. The cdtA gene reported by Pickett et al. was not found among S. dysenteriae, V. cholerae O1 and V. parahaemolyticus. To further investigate the distribution of the cdtA gene among a large number of Shigella spp. (S. dysenteriae, S. flexneri, S. boydii and S. sonnei), and among Vibrio spp. (Vibrio cholerae O1, V. cholerae O139 and V. parahaemolyticus) by colony hybridization test, we constructed a cdtA gene specific DNA probe by amplifying the cdtA gene by PCR with primers designed from the nucleotide sequence of the cdtA gene reported by Scott and Kaper. The cdtA gene reported by Scott and Kaper was found to occur among eight of the 35 strains of S. dysenteriae and one of the 100 strains of S. sonnei, but was not found among other species of Shigella or among the Vibrio species examined. From one cdtA gene-positive S. dysenteriae strain that showed cytolethal distending toxin (CDT) activity on Chinese hamster ovary cells, we cloned and sequenced the entire cdt gene comprising cdtA, cdtB and cdtC genes.(ABSTRACT TRUNCATED AT 250 WORDS)