SHIGELLA

Shigella is a genus of gamma proteobacteria in the family Enterobacteriaceae. Shigellae are Gram-negative, nonmotile, non-spore forming, rod-shaped bacteria, very closely related to Escherichia coli.

Shigella sp.

Shigella sp.

Shigella were discovered over 100 years ago by the Japanese microbiologist, Shiga, for whom the genus is named. There are four species of Shigella: S. boydii, S. dysenteriae, S. flexneri, and S. sonnei. Shigella sonnei, also known as Group D Shigella, accounts for over two-thirds of the shigellosis in the United States.

Shigella flexneri, or Group B Shigella, accounts for almost all of the rest. Other types of Shigella are rare in this country, although they are important causes of disease in the developing world.

Figure: Several media have been designed to selectively grow enteric bacteria and allow differentiation of Salmonella and Shigella from E. coli. The primary plating media shown here are eosin methylene blue (EMB) agar, MacConkey agar, ENDO agar, Hektoen enteric (HE) agar and Salmonella-Shigella (SS) agar.

http://www.textbookofbacteriology.net/Shigella.html

Diagnosis.

Environment: water

Microorganism: Gram - rod

Spore former: NO

Motile: NO

Susceptibility: anyone

Communicability: infectious, fecal-oral transmission

Exposure: contaminated food or water

Incubation: 12-15 hours

Primary Treatment: antibiotics, fluid replacement

Prognosis: excellent with treatment

Quarantine recommended: NO

Use as a biological weapon: NO

Shigella dysenteriae.

IDENTIFICATION

S.Dysenteriae is a facultative anaerobic, rod-shaped bacteria. Laboratory indicators: non-motile Lysine: - Lactose: - anaerogenic (no gas production from carbohydrates)

http://microbes.historique.net/dysenteriae.html

Shigella dysenteriae.

Bacteria (domain); Proteobacteria (phylum); Gamma Proteobacteria (class); Enterobacteriales (order); Enterobacteriaceae (family); Shigella (genus); Shigella boydii (spesies)

Shigella boydii is a bacillary (rod-shaped) gram-negative bacterium that does not form spores and is usually nonmotile.

Habitat: S. boydii inhabits the intestine and rectum of humans and other primates. It can survive in feces and soil and/or food/water contaminated with fecal matter. For example, in Guadalajara, Mexico, Salmonella and Shigella species were found in freshly squeezed orange juice, oranges, and wiping cloths found in public markets and street booths.

Shigella boydii

Shigella boydiiCell Structure: Shigella's structural characteristics follow that of Gram-negative bacteria. Most research would agree that Shigella are nonmotile but some evidence suggests that they do in fact have flagella, although motility is not necessary for infection of intestine. The flagella tend to be on one pole of the cell and about 10 microns in length and 12-14nm in diameter.

Metabolism: S. boydii, when found in the intestine, go though anaerobic metabolic pathways but can survive outside of the body due to its ability to utilize aerobic pathways. More specifically, S. boydii, typically does not have oxidase enzymes but rather catalase enzymes.Methyl red testing is positive, meaning that the bacteria uses a mixed acid fermentation pathway. Voges–Proskauer and Simmons’ citrate reactions are negative, meaning that this organism does not utilize the butylene glycol pathway or produce acetoin. Lysine decarboxylase, arginine dihydrolase and ornithine decarboxylase are not present. S. boydii does not produce H2S, does not hydrolyze urea. Carbohydrates are usually fermented and these include glucose (in the absence of gas production), D-mannitol, arabinose, trehalose and mannose.

http://www.microbewiki.kenyon.edu

Shigella sonnei

Domain: Bacteria Phylum: Proteobacteria Class: Gamma proteobacteria Order: Enterobacteriales Family: Enterobacteriaceae Genus: Shigella Species:Shigella sonnei.

Shigella sonnei is a non-motile (don’t have flagella), nonspore-forming, facultative anaerobic Gram-negative bacterium. Shigella sonnei is a rod-shape bacterium and is lactose-fermenting bacterium causing dysentery.

Shigella sonnei is extremely fragile in experimental settings. Its natural habitat is in a low pH environment such as the human gastrointestinal tract. Its optimal environmental temperature is 37 degrees Celsius, similar to the temperature in the human body. Therefore, human’s gastrointestinal tract appears to be the only found natural host of Shigella sonnei that we know so far.

Shigella flexneri

Domain:Bacteria, Phylum:Proteobacteria, Class:Gamma Proteobacteria, Order:Enterobacteriales, Family:Enterobacteriaceae, Genus:Shigella,

Species:S. flexneri

Shigella flexneri is a species of Gram-negative bacteria in the genus Shigella that can cause diarrhea in humans. There are several different serogroups of Shigella; S. flexneri belongs to group B.

S. flexneri infections can usually be treated with antibiotics although some strains have become resistant.

Shigella flexneri

Shigella flexneri is a non-motile, non-spore forming, rod-shaped bacterium that is physiologically similar to Shigella dysenteriae, Shigella boydii, and Escherichia coli.

It is important because it causes shigellosis, an acute bloody diarrhea. Shigella flexneri is the most common cause of the endemic form of shigellosis, and the endemic form is the cause of most Shigellosis-related deaths.

While not much of a problem in developed countries, Shigella flexneri (specifically Shigella flexneri 2a) is a major public health concern in developing countries. Shigella was recognized as the cause of bacillary dysentery in the 1890s by Shiga, hence the genus name (Nato et al.). Shigella flexneri 2a strain 301 was isolated and sequenced by Jin et al. They isolated the bacterium from a shigellosis patient in China in 1984.

Shigella flexneri

Shigella flexneri is a facultative anaerobe. It makes ATP via aerobic respiration in the presence of oxygen and via fermentation in the absence of oxygen. Although it is closely related to Escherichia coli, Shigella flexneri can be differentiated because it fails to ferment lactose or decarboxylate lysine (Jin et al.)Shigella flexneri is prevalent in developing countries because sanitation is poor. The bacterium is found in the feces of infected individuals, so water polluted with feces can act as a route of infection (Huang and Zhou).