Helicobacter pylori, previously known as Campylobacter pylori, is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach. Its helical shape is thought to have evolved in order to penetrate the mucoid lining of the stomach and thereby establish infection. The bacterium was first identified in 1982 by the Australian doctors Barry Marshall and Robin Warren. H. pylori has been associated with cancer of the mucosa-associated lymphoid tissue in the stomach, esophagus, colon, rectum, or tissues around the eye, and of lymphoid tissue in the stomach.
Helicobacter is a genus of Gram-negative bacteria possessing a characteristic helical shape. They were initially considered to be members of the genus Campylobacter, but in 1989, Goodwin et al. published sufficient reasons to justify the new genus name Helicobacter. The genus Helicobacter contains about 35 species.
Murine coronavirus (M-CoV) is a virus in the genus Betacoronavirus that infects mice. Belonging to the subgenus Embecovirus, murine coronavirus strains are enterotropic or polytropic. Enterotropic strains include mouse hepatitis virus (MHV) strains D, Y, RI, and DVIM, whereas polytropic strains, such as JHM and A59, primarily cause hepatitis, enteritis, and encephalitis. Murine coronavirus is an important pathogen in the laboratory mouse and the laboratory rat. It is the most studied coronavirus in animals other than humans, and has been used as an animal disease model for many virological and clinical studies.
Chromobacterium violaceum is a Gram-negative, facultative anaerobic, non-sporing coccobacillus. It is motile with the help of a single flagellum which is located at the pole of the coccobacillus. Usually, there are one or two more lateral flagella as well. It is part of the normal flora of water and soil of tropical and sub-tropical regions of the world. It produces a natural antibiotic called violacein, which may be useful for the treatment of colon and other cancers. It grows readily on nutrient agar, producing distinctive smooth low convex colonies with a dark violet metallic sheen. Some strains of the bacteria which do not produce this pigment have also been reported. It has the ability to break down tarballs.
This is a timeline of the events relating to the discovery that peptic ulcer disease and some cancers are caused by H. pylori. In 2005, Barry Marshall and Robin Warren were awarded the Nobel Prize in Physiology or Medicine for their discovery that peptic ulcer disease (PUD) was primarily caused by Helicobacter pylori, a bacterium with affinity for acidic environments, such as the stomach. As a result, PUD that is associated with H. pylori is currently treated with antibiotics used to eradicate the infection. For decades prior to their discovery, it was widely believed that PUD was caused by excess acid in the stomach. During this time, acid control was the primary method of treatment for PUD, to only partial success. Among other effects, it is now known that acid suppression alters the stomach milieu to make it less amenable to H. pylori infection.
Estimates place the worldwide risk of cancers from infectious causes at 16.1%. Viral infections are risk factors for cervical cancer, 80% of liver cancers, and 15–20% of the other cancers. This proportion varies in different regions of the world from a high of 32.7% in Sub-Saharan Africa to 3.3% in Australia and New Zealand. Helicobacter pylori is associated with stomach cancer, and Mycobacterium, some other bacteria and parasites also have an effect.
Helicobacter pullorum is a bacterium in the Helicobacteraceae family, Campylobacterales order. It was isolated from the liver, duodenum, and caecum of broiler and layer chickens, and from humans with gastroenteritis. It is a nongastric urease-negative Helicobacter species colonizing the lower bowel.
Helicobacter canis is a bacterium in the Helicobacteraceae family, Campylobacterales order. Its type strain is NCTC 12739T. It colonises the lower bowel, but is also present in cases of hepatitis. Besides infecting dogs, this bacterium is known to cause infections in immunocompromised humans.
Helicobacter bilis is a bacterium in the Helicobacteraceae family, Campylobacterales order. It is a fusiform bacterium with three to 14 multiple bipolar sheathed flagella and periplasmic fibers wrapped around the cell. It is resistant to cephalothin and nalidixic acid, but sensitive to metronidazole. Like Helicobacter hepaticus, it colonizes the bile, liver, and intestine of mice, and is associated with multifocal chronic hepatitis and hepatocellular tumors.
Helicobacter rodentium is a bacterium in the Helicobacteraceae family, Campylobacterales order. It is a spiral-shaped bacterium with a bipolar, single, nonsheathed flagellum. It is resistant to cephalothin and nalidixic acid. Its type strain is MIT 95-1707. Its name refers to the species first being isolated from mice.
Helicobacter muridarum is a bacterium in the Helicobacteraceae family, Campylobacterales order. It is microaerophilic and helical and was first isolated from the intestinal mucosa of rodents, hence its name. It is characterised by the presence of 9 to 11 periplasmic fibers which appear as concentric helical ridges on the surface of each cell. The cells are motile and have bipolar tufts of 10 to 14 sheathed flagella. These bacteria are nutritionally fastidious and physiologically similar to other Helicobacter species and Wolinella succinogenes, but can be differentiated from these organisms by their unique cellular ultrastructure. ST1T is its type strain.
Helicobacter felis is a bacterial species in the Helicobacteraceae family, Campylobacterales order, Helicobacter genus. This bacterium is Gram-negative, microaerophilic, urease-positive, and spiral-shaped. Its type strain is CS1T. It can be pathogenic.
Helicobacter acinonychis is a bacterium in the Helicobacteraceae family, Campylobacterales order. It was first isolated from cheetahs with gastritis, so has been associated with this disease in this particular species and others of its kind. It is Gram-negative, spiral-shaped, and grows under microaerophilic conditions. The type strain is 90-119.
Helicobacter canadensis is a bacterium in the Helicobacteraceae family, Campylobacterales order, first isolated from humans with diarrhea. Its genome has been sequenced.
Helicobacter trogontum is a bacterium in the Helicobacteraceae family, Campylobacterales order. It was first isolated from rat intestine. It is Gram-negative, its cells are rod-shaped with pointed ends, and its protoplasmic cylinder is entwined with periplasmic fibers. It is microaerophilic. The type strain is LRB 8581.
Helicobacter pametensis is a bacterium in the Helicobacteraceae family, Campylobacterales order. It was first isolated from bird and swine faeces. Its cells are motile and possess one subterminal sheathed flagellum at each end.
Helicobacter anseris is a bacterium in the Helicobacteraceae family, Campylobacterales order. It is Gram-negative, microaerophilic, spiral to curve-shaped, being first isolated from the faeces of geese.
Helicobacter brantae is a bacterium in the Helicobacteraceae family, Campylobacterales order. It is Gram-negative, microaerophilic, spiral to curve-shaped, being first isolated from the faeces of geese.
Helicobacter typhlonius is a Gram-negative bacterium and opportunistic pathogen found in the genus Helicobacter. Only 35 known species are in this genus, which was described in 1982. H. typhlonius has a small number of close relatives, including Helicobacter muridarum, Helicobacter trogontum, and Helicobacter hepaticus, with the latter being the closest relative and much more prevalent.
Helicobacter cetorum is a Gram-negative, microaerophilic, spiral (helical) bacterium that is usually found in the stomachs of whales and dolphins. Based on 16S rRNA sequencing, its genome is very similar to that of Helicobacter pylori in that it can cause gastric disease in these animals. Originally isolated among Atlantic white-sided dolphins and Beluga whales in 2000, H. cetorum has been associated with hemorrhages throughout its entire gastrointestinal tract, but its role has not yet been discovered. Prior to the discovery of H. cetorum, there have not been any other Helicobacter species reported in dolphins.
