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image at: emedicine.medscape.com/ article/962643
image at: emedicine.medscape.com/ article/962643


Vibrio cholerae


Classification: Bacteria; Proteobacteria; Gammaproteobacteria; Vibrionales; Vibrionaceae; Vibrio.

  • gram negative
  • comma shaped bacteria
  • single polar flagellum used for movement.
  • facultative anaerobic bacteria (they can survive with or without oxygen).

´╗┐There are several strains of V. cholerae, some pathogenic, some not. The most wide sweeping pathogenic strain is the Vibrio cholerae serotype O1 El Tor N16961 strain which causes cholera (an acute diarrheal illness that can cause serious dehydration and in some cases death). The El Tor strain was active in the pandemic between the 1960s and 1970s and in the most recent pandemic in 1992 when the latest pathogenic strain was discovered, serotype O139. During this pandemic both strains showed resistance to multiple anti-biotics.


History

In the middle of the 19th century cholera had arrived in Italy. At this time not much was known about cholera and what caused it so a scientist called Filippo Pacini took the chance to discover the basis of the disease. He performed autopsies on the bodies of victims and several histological analyses on the mucosal, inner lining of the intestine. He studied the samples under microscopes and managed to isolate a comma-shaped bacillus, which he named Vibrio. His findings were first published in a paper in the year 1854, but for many years this paper went unknown.

Thirty years later, Robert Koch, unaware of Pacinis findings, started to research the bacteria responsible for cholera. He also found a comma-shaped bacillus but was not sure if it caused cholera or was a consequence of the disease. To find out he isolated the bacteria, grew a culture of it and infected animals with the microorganism and observed to see if the disease would develope. Nothing happened

Ecology

V. cholerae thrives in water (surface water),both fresh and marine. Both pathogenic and non pathogenic strains co-exsist in an aquatic environment which is thought to be the reason for so many genetic varieties of the bacteria. The connection between humans and the pathogenic strains is through water, most commonly in areas that dont have good water purifying systems.


Pathology

V. cholerae enters the human body through injesting contaminated food or water. The bacteria travels to the small intestine where it fixes itself to the villi of intestinal cells, multiplies and releases cholera toxin. Cholera toxin is a enterotoxin, made up of five B-subunits that form a pore to fit one A-subunit.
Once cholera toxin had been released in the body there is a physiological response of the mucosal lining in the intestine to secrete fluids. This then causes the characteristic vomiting and diarhea of cholera. The severity of the vomiting and diarhea often leads to death if untreated as the body becomes extremely dehydrated as a result.
Treatment usually involves rehydration and replaceent of electrolytes which are essential for the body to carry out all the biochemical processes needed to stay alive. As its hard to rehydrate people living in countries with poor water quality, medical aid is often needed aswell.
A person needs to injest alot of V.cholerae before they show any symptoms of cholera.

Uses in Biotechnology

Non-toxic B-subunits can be used in cellular and molecular biology. They can be used to dectect nerve locations within the body when attached to a fluorescent protein. As a result the non-toxic products of V. cholerae are often used in an opperating room when small nerves need to be found.


















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