Cytolethal distending toxin (CDT): Genetic diversity, structure and role in diarrheal disease

In 1987, cytolethal distending toxin (CDT) was discovered by Johnson and Lior as a new type of protein toxin produced by certain strains of Escherichia coli, which is different from heat-labile enterotoxin (LT) produced by enterotoxigenic E. coli. Although LT causes only cell elongation, CDT causes cell elongation, cell distention, irreversible cell cycle arrest, and consequently, death of the cultured mammalian cells. Recently, CDT was recognized as a new family of bacterial toxin, as a genotoxin, produced by a diverse group of gram-negative bacteria, all of which are related to mucosal infection. Although tremendous efforts have been made to study the structure and mode of action of CDT, its role in bacterial pathogenesis still remains unclear. In this review, we focus mainly on CDT produced by enteric bacteria and describe the history of CDT, their gene and protein structure, structure-function relationship, and its mode of action particularly how CDT contributes to the gastrointestinal infections.