Helicobacter

Taxobox
color = lightgrey
name = "Helicobacter"

---

image_width = 240px
image_caption = Scanning electron micrograph of "Helicobacter" bacteria.
regnum = Bacteria
phylum = Proteobacteria
classis = Epsilon Proteobacteria
ordo = Campylobacterales
familia = Helicobacteraceae
genus = "Helicobacter"
genus_authority = Goodwin "et al." 1989
subdivision_ranks = Species
subdivision = "H. acinonychis"
"H. anseris"
"H. aurati"
"H. bilis"
"H. bizzozeronii"
"H. brantae"
"H. canadensis"
"H. canis"
"H. cholecystus"
"H. cinaedi"
"H. cynogastricus"
"H. felis"
"H. fennelliae"
"H. ganmani"
"H. hepaticus"
"H. mesocricetorum"
"H. marmotae"
"H. muridarum"
"H. mustelae"
"H. pametensis"
"H. pullorum"
"H. pylori"
"H. rappini"
"H. rodentium"
"H. salomonis"
"H. trogontum"
"H. typhlonius"
"H. winghamensis"

"Helicobacter" is a genus of Gram-negative bacteria possessing a characteristic helix shape. They were initially considered to be members of the "Campylobacter" genus, but since 1989 they have been grouped in their own genus. [cite journal | author = Goodwin CS, Armstrong JA, Chilvers T, "et al" | title = Transfer of "Campylobacter pylori" and "Campylobacter mustelae" to "Helicobacter" gen. nov. as "Helicobacter pylori" comb. nov. and "Helicobacter mustelae" comb. nov., respectively.| journal = Int. J. Syst. Bacteriol.| year = 1989| volume = 39| issue = | pages = 397–405| url= ] [cite journal | author = Vandamme P, Falsen E, Rossaq R, "et al" | title = Revision of "Campylobacter", "Helicobacter", and "Wolinella" taxonomy: emendation of generic descriptions and proposal of "Arcobacter" gen. nov. | journal = Int. J. Syst. Bacteriol.| year = 1991| volume = 41| issue = | pages = 88–103 | url= http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1704793&dopt=Citation] cite book | author = Yamaoka Y (editor). | title = Helicobacter pylori: Molecular Genetics and Cellular Biology | publisher = Caister Academic Press | year = 2008 | url=http://www.horizonpress.com/hpl2 | id = [http://www.horizonpress.com/hpl2 ISBN 978-1-904455-31-8 ] ]

Some species have been found living in the lining of the upper gastrointestinal tract, as well as the liver of mammals and some birds. [cite book | author = Ryan KJ, Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | publisher = McGraw Hill | year = 2004 | isbn = 0-8385-8529-9 ] . The most widely known species of the genus is "H. pylori" which infects up to 50% of the human population.cite book | author = Yamaoka Y (editor). | title = Helicobacter pylori: Molecular Genetics and Cellular Biology | publisher = Caister Academic Press | year = 2008 | url=http://www.horizonpress.com/hpl2 | id = [http://www.horizonpress.com/hpl2 ISBN 978-1-904455-31-8 ] ] Some strains of this bacterium are pathogenic to humans as it is strongly associated with peptic ulcers, chronic gastritis, duodenitis, and stomach cancer. It also serves as the type species of the genus.

"Helicobacter" spp. are able to thrive in the very acidic mammalian stomach by producing large quantities of the enzyme urease, which locally raises the pH from ~2 to a more biocompatible range of 6 to 7. [cite journal | author = Dunn BE, Cohen H, Blaser MJ| title = "Helicobacter pylori". | journal = Clin Microbiol Rev. | year = 1997 | volume = 10 | issue = | pages = 720–741 | url= http://cmr.asm.org/cgi/reprint/10/4/720?] Bacteria belonging to this genus are usually susceptible to antibiotics such as penicillin, are microaerophilic (require small amounts of oxygen), and are fast-moving with their flagella. [cite journal | author = Hua JS, Zheng PY, Ho B | title = Species differentiation and identification in the genus of "Helicobacter". | journal = World Journal of Gastroenterology. | year = 1999 | volume = 5 | issue = 1 | pages = 7–9 | url=http://www.wjgnet.com/1007-9327/5/7.pdf] cite book |chapterurl=http://www.horizonpress.com/hpl2 |author= Rust et al|year=2008|chapter=Helicobacter Flagella, Motility and Chemotaxis | title = Helicobacter pylori: Molecular Genetics and Cellular Biology (Yamaoka Y, ed.)| publisher = Caister Academic Press | year = 2008 | id = [http://www.horizonpress.com/hpl2 ISBN 978-1-904455-31-8 ] ]

=Helicobacter Facts. [cite book | author = Kathleen Park Talaro | title = Foundations in Microbiology | edition = 6th ed. | publisher = McGraw Hill | year = 2006 | isbn = 0072994959 ] =

Curved cells discovered in 1979 in stomach biopsied specimens.

Causes 90% of stomach & duodenal ulcers.

People with type O blood have a 1.5-2X higher rate of ulcers.

Produces large amounts of urease.

Infection common especially in lower socioeconomic class/developing nations.

Humans primary reservoir.

Person-to-person spread via fecal-oral route.

Ubiquitous, no seasonal incidence.

Diseases

In 1994, the World Health Organization’s International Agency for Research on Cancer (IARC) classified H. pylori as a Group 1 carcinogen. This decision was based on the results of numerous studies that confirmed the association between H. pylori infection and gastric adenocarcinoma. H. pylori infection also significantly increases the risk of gastric lymphoma of mucosa-associated lymphoid tissue (MALT) (Suerbaum, 2002).

While "H. pylori" remains the most medically important bacterial inhabitant of the human stomach, other species of the genus "Helicobacter" have been identified in other mammals and some birds, and some of these can infect humans. [cite book
author=Stuart L. Hazell; Mobley, Harry L. T.; George L. Mendz
title="Helicobacter pylori": Physiology and Genetics
publisher=American Society Microbiology
location=
year=2001
isbn=1-55581-213-9
accessdate=] "Helicobacter" species have also been found to infect the livers of certain mammals and to cause liver disease.cite journal
author=Starzyñska T, Malfertheiner P
title="Helicobacter" and digestive malignancies
journal=Helicobacter
volume=11 Suppl 1
pages=32–5
year=2006
month=October
pmid=16925609
doi=10.1111/j.1478-405X.2006.00431.x]

Diagnosis

H. pylori infection can be confirmed by invasive or noninvasive methods. Invasive tests require upper esophagogastroduodenal (EGD) endoscopy, which is considered the reference method of diagnosis. During endoscopy, biopsy specimens of the stomach and duodenum are obtained, and the diagnosis of H. pylori can be made by urease testing, histology and/or culture. If possible, noninvasive testing is done before tissue testing.

H. pylori stool antigen (HpSA) testing is based on monoclonal antibody immunochromatography of stool samples. This testing method identifies active infection and can be used to detect eradication after treatment. A sensitivity and specificity range of 92–98% is reported in the literature for stool antigen testing.

Serological assays (blood serum) measure specific H. pylori immunoglobulin G (IgG) antibodies that can determine if an individual has been infected. The sensitivity and specificity of these assays range from 80–95%, depending on the assay used. Serological testing has been the mainstay of H. pylori diagnosis, particularly in primary care, due to the accessibility, rapid results and low cost of this testing method.

Urease test, Urease Breath Test (UBT) (positive in as little as 2 hours) [cite journal | author = Robert P H Logan, Marjorie M Walker| title = "Epidemiology and diagnosis of Helicobacter pylori infection ". | journal = BMJ 2001;323:920-922 ( 20 October ) | year = 2001| volume = 323| issue = | pages = –741 | url= http://www.bmj.com/cgi/content/full/323/7318/920| pmid = 11668141| doi = 10.1136/bmj.323.7318.920]

Treatment

Therapy is with tetracycline, metronidazole, azithromycine, bismuth (Peptobismol).

References

ee also

*"Helicobacter pylori"

External links

* [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=209&lvl=3&lin=f&keep=1&srchmode=1&unlock List of species in "Helicobacter", with links to sequence information]