Vibrio

Vibrio is a genus of Gram-negative bacteria, possessing a curved-rod (comma) shape, several species of which can cause foodborne infection, usually associated with eating undercooked seafood. Typically found in salt water, Vibrio species are facultative anaerobes that test positive for oxidase and do not form spores. All members of the genus are motile and have polar flagella with sheaths. Vibrio species typically possess two chromosomes, which is unusual for bacteria. Each chromosome has a distinct and independent origin of replication, and are conserved together over time in the genus. Recent phylogenies have been constructed based on a suite of genes (multilocus sequence analysis). O. F. Müller (1773, 1786) described eight species of the genus Vibrio (included in Infusoria), three of which were spirilliforms. Some of the other species are today assigned to eukaryote taxa, e.g., to the euglenoid Peranema or to the diatom Bacillaria. However, Vibrio Müller, 1773 became regarded as the name of a zoological genus, and the name of the bacterial genus became Vibrio Pacini, 1854. Filippo Pacini isolated micro-organisms he called 'vibrions' from cholera patients in 1854, because of their motility. Several species of Vibrio are pathogens. Most disease-causing strains are associated with gastroenteritis, but can also infect open wounds and cause sepsis. They can be carried by numerous marine animals, such as crabs or prawns, and have been known to cause fatal infections in humans during exposure. Risk of clinical disease and death increases with certain factors, such as uncontrolled diabetes, elevated iron levels (cirrhosis, sickle cell disease, hemochromatosis), and cancer or other immunocompromised states. Pathogenic Vibrio species include V. cholerae (the causative agent of cholera), V. parahaemolyticus, and V. vulnificus. V. cholerae is generally transmitted by contaminated water. Pathogenic Vibrio species can cause foodborne illness (infection), usually associated with eating undercooked seafood. The pathogenic features can be linked to quorum sensing, where bacteria are able to express their virulence factor via their signalling molecules. V. vulnificus outbreaks commonly occur in warm climates and small, generally lethal, outbreaks occur regularly. An outbreak occurred in New Orleans after Hurricane Katrina, and several lethal cases occur most years in Florida. As of 2013 in the United States, Vibrio infections as a whole were up 43% when compared with the rates observed in 2006–2008. V. vulnificus, the most severe strain, has not increased. Foodborne Vibrio infections are most often associated with eating raw shellfish. V. parahaemolyticus is also associated with the Kanagawa phenomenon, in which strains isolated from human hosts (clinical isolates) are hemolytic on blood agar plates, while those isolated from nonhuman sources are not hemolytic. Many Vibrio species are also zoonotic. They cause disease in fish and shellfish, and are common causes of mortality among domestic marine life.