Vibrio cholerae is a gram negative comma-shaped bacterium with a polar flagellum that causes cholera in humans. V. cholerae belongs to the gamma subdivision of the Proteobacteria. Classical and El Tor are the two types of V. Cholerae identified by hemaggluttination testing.
El Tor is found throughout the world, while the classical biotype is found only in Bangladesh. It was first isolated as the cause of cholera by Italian anatomist Filippo Pacini in 1854; however, this discovery was not widely known until Robert Koch publicized the knowledge and the means of fighting the disease.
The symptoms of cholera are encoded in the genome of a temperate bacteriophage. This strain has furthered the understanding of the genetic and phenotypic diversity found within the species V. cholerae. Sequencing of additional strains, subtractive hybridization studies, and the introduction of new model systems have also contributed to the identification of novel sequences and pathogenic mechanisms associated with other strains.
They are interesting targets to detect and to study V. cholerae infections. Most of the virulence genes are located in two pathogenicity plasmids which are organized as prophages: CTX and TCP. These two elements are required to cause infections.
CTX plasmid is composed of genes involved in toxin production. It is divided into two regions: CORE encoding toxins, and RS2 encoding proteins that catalyze the integration and the replication of CTX prophage in the V. cholerae chromosome. The plasmid contains genes that were strongly studied because of their biological and medical importance.