Vibrio бактериялары және олардың қоздыратын аурулары

Genus of bacteria and the disease it can cause

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. Being highly salt tolerant and unable to survive in fresh water, Vibrio spp. are commonly found in various salt water environments. Vibrio spp. are facultative anaerobes that test positive for oxidase and do not form spores. 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). 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.

The genus Vibrio contains a large number of species, and these vary somewhat in their biochemical characteristics. Colony, morphological, physiological, and biochemical characteristics of the genus Vibrio are shown in the Table below. 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 after 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. When ingested Vibrio bacteria can primarily result in watery diarrhea along with other secondary symptoms. The pathogenic features can be linked to quorum sensing, where bacteria are able to express their virulence factor via their signaling 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,

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. Water loss can lead to dehydration which can be mild to moderate to severe. Moderate to severe dehydration requires immediate treatment. V. cholerae is the most common pathogen that causes cholera. The gold standard for detecting cholera is through cultures of stool samples or rectal swabs. Identification is then done through microscopy or by agglutination of antibodies.

Vibriosis is a sign of a more severe Vibrio infection. Common causes of vibriosis include consumption of raw or undercooked seafood, primarily oysters, or wound exposure to sea water. The majority of V. parahemolyticus infections can be self limiting and symptoms include diarrhea, nausea, headaches, fever and chills. V. vulnificus can lead to a more serious disease, particularly in wound infection which can turn into necrotizing fasciitis. V. parahaemolyticus is the most common pathogen in vibriosis, however V. vulnificus is more common in people who have certain risk factors like older age, liver disease or diabetes mellitus. Like all vibrio diagnosis, vibriosis can also be determined in stool cultures. V. parahemolyticus and V. vulnificus will form green colonies. Patients who cannot tolerate oral fluid replacement may require intravenous fluid therapy. Although most Vibrio species are sensitive to antibiotics such as doxycycline or ciprofloxacin, antibiotic therapy does not shorten the course of the illness or the duration of pathogen excretion. However, if the patient is ill and has a high fever or an underlying medical condition, oral antibiotic therapy with doxycycline or ciprofloxacin can be initiated.

Prevention of vibriosis is mostly effected in food processing. Food items, mostly seafood, that commonly contain vibrio organisms are regularly controlled. The water that seafood is fished or farmed from is analyzed to determine microorganism content. Food processing methods like pasteurization and high pressure are used to eliminate microorganisms and pathogens. Aliivibrio fischeri (or V. fischeri) is known for its mutualistic symbiosis with the Hawaiian bobtail squid, which is dependent on microbial luminescence.

The "typical", early discovered Vibrio species, such as V. cholerae, have a single polar flagellum (monotrichous) with sheath. Some species, such as V. parahaemolyticus and V. alginolyticus, have both a single polar flagellum with sheath and thin flagella projecting in all directions (peritrichous), and the other species, such as V. fischeri, have tufts of polar flagella with sheath (lophotrichous).

Motility is very important for Vibrio spp for infection. Research has shown that a variety of Vibrios mutants that are defective in flagella synthesis or non motile are defective in infection. Loss of motility in Vibrio has shown impaired colonization and adherence to host's intestines. For a recipient bacterium to bind, take up, and recombine exogenous DNA into its chromosome, it must become competent, that is, enter a special physiologic state. The DNA uptake process of naturally competent V. cholerae involves an extended competence induced pilus and a DNA binding protein that acts as a ratchet and reels DNA into the periplasm. Natural transformation has also been described for V. fisheri, V. vulnificus and V. parahaemolyticus.

V. cholerae has been used in discoveries of many bacterial small RNAs. Using sRNA Seq and Northern blot candidate sRNAs were identified and characterised as IGR sRNA (intragenic region), AS sRNAs (transcribed from the antisense strand of the open reading frame (ORF) and ORF derived. One of the candidates from this study, IGR7, was shown to be involved in carbon metabolism and later renamed MtlS RNA. Other sRNAs identified in V. cholerae through genetic screens and computational methods include Qrr RNA, Vibrio regulatory RNA of OmpA, MicX sRNA, Vibrio cholerae ToxT activated RNAs, tfoR RNA, and VqmR sRNA.