Abstract
Cholera is a severe form of watery diarrhea caused by Vibrio cholerae toxigenic strains. Typically, the toxigenic variants of V. cholerae harbor a bacteriophage, cholera toxin phage, integrated in their genome. The ctxAB genes from the phage genome encode the cholera toxin, which is responsible for the major clinical symptoms of the disease. Although ctxAB genes are crucial to V. cholerae strains for cholera manifestation, the genetic structure of cholera toxin phage, DNA sequence of its genes, spatial organization in the host genome and its satellite phage content are not homogenous between V. cholerae biotypes—classical and El Tor. Differences in cholera toxin phage and its genes play a significant role in the identification of V. cholerae biotypes and in the understanding of their pathogenic and epidemic potentials. Here, we present an account of the variations of cholera toxin phage and its genes in V. cholerae biotypes as well as their usefulness in the identification of classical and El Tor strains.
Highlights
Vibrio cholerae is an ancient human pathogen that causes a severe form of diarrhea known as cholera
CtxAB genes are crucial to V. cholerae strains for cholera manifestation, the genetic structure of cholera toxin phage, DNA sequence of its genes, spatial organization in the host genome and its satellite phage content are not homogenous between V. cholerae biotypes—classical and El El Tor CT (Tor)
We summarize our knowledge of the structural and functional diversity of Cholera Toxin Phage (CTXφ) and its genes in the genome of classical and El Tor strains and their applications in differentiating these two biotypes
Summary
Vibrio cholerae is an ancient human pathogen that causes a severe form of diarrhea known as cholera. Based on the biochemical and phenotypic differences among V. cholerae strains from serogroup O1, two clearly distinct biotypes (a nominate form or subspecies), ‘classical’ and ‘El Tor’, have been described. In addition to the phenotypic differences, structure of CTXφ and its genes in classical and El Tor strains vary significantly and these differences have long been used to differentiate V. cholerae biotypes. CTXφs are known to differ in their arrangement, their choice of host chromosome type (small and/or large) for integration, and their copy number in each chromosome of the strains of the two biotypes. We summarize our knowledge of the structural and functional diversity of CTXφ and its genes in the genome of classical and El Tor strains and their applications in differentiating these two biotypes
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