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Shigella
''Shigella'' is a genus of bacteria that is Gram-negative, facultative anaerobic, non-spore-forming, nonmotile, rod-shaped and genetically closely related to ''E. coli''. The genus is named after Kiyoshi Shiga, who first discovered it in 1897. The causative agent of human shigellosis, ''Shigella'' causes disease in primates, but not in other mammals. It is only naturally found in humans and gorillas. During infection, it typically causes dysentery. ''Shigella'' is one of the leading bacterial causes of diarrhea worldwide, causing an estimated 80–165 million cases. The number of deaths it causes each year is estimated at between 74,000 and 600,000. It is one of the top four pathogens that cause moderate-to-severe diarrhea in African and South Asian children. Classification ''Shigella'' species are classified by three serogroups and one serotype: * Serogroup ''A'': ''S. dysenteriae'' (15 serotypes) * Serogroup ''B'': ''S. flexneri'' (9 serotypes) * Serogroup ''C'': ''S. boydii' ...
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Shigellosis
Shigellosis is an infection of the intestines caused by ''Shigella'' bacteria. Symptoms generally start one to two days after exposure and include diarrhea, fever, abdominal pain, and feeling the need to pass stools even when the bowels are empty. The diarrhea may be bloody. Symptoms typically last five to seven days and it may take several months before bowel habits return entirely to normal. Complications can include reactive arthritis, sepsis, seizures, and hemolytic uremic syndrome. Shigellosis is caused by four specific types of ''Shigella''. These are typically spread by exposure to infected feces. This can occur via contaminated food, water, or hands or sexual contact. Contamination may be spread by flies or when changing diapers (nappies). Diagnosis is by stool culture. The risk of infection can be reduced by properly washing the hands. There is no vaccine. Shigellosis usually resolves without specific treatment. Sufficient fluids by mouth and rest is recommended. Bismu ...
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Shigella Sonnei
''Shigella sonnei'' is a species of ''Shigella''. Together with ''Shigella flexneri'', it is responsible for 90% of shigellosis cases. ''Shigella sonnei'' is named for the Danish bacteriologist Carl Olaf Sonne. It is a Gram-negative, rod-shaped, nonmotile, non-spore-forming bacterium. Pathophysiology This species polymerizes host cell actin. Evolution This species is clonal and has spread worldwide. Analysis of 132 strains has shown that they originated from a common ancestor in Europe around 1500 AD. Causes "Group D" ''Shigella'' bacteria cause shigellosis. Those infected with the bacteria release it into their stool, thus causing possibility of spread through food or water, or from direct contact to a person orally. Having poorly sanitized living conditions or contaminated food or water contributes to contracting the disease. People at risk Infants and toddlers, the elderly, travelers, and ill people are susceptible to the most severe symptoms of ''S. sonnei'' disease. Shig ...
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Shigella Flexneri
''Shigella flexneri'' is a species of Gram-negative bacteria in the genus ''Shigella'' that can cause diarrhea in humans. Several different serogroups of ''Shigella'' are described; ''S. flexneri'' belongs to group ''B''. ''S. flexneri'' infections can usually be treated with antibiotics, although some strains have become resistant. Less severe cases are not usually treated because they become more resistant in the future. Shigella are closely related to ''Escherichia coli'', but can be differentiated from ''E.coli'' based on pathogenicity, physiology (failure to ferment lactose or decarboxylate lysine) and serology. Discovery The species was named after the American physician Simon Flexner; the genus Shigella is named after Japanese physician Kiyoshi Shiga, who researched the cause of dysentery. Shiga entered the Tokyo Imperial University School of Medicine in 1892, during which he attended a lecture by Dr. Shibasaburo Kitasato. Shiga was impresse ...
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Shigella Boydii
''Shigella boydii'' is a Gram-negative bacterium of the genus ''Shigella''. Like other members of the genus, ''S. boydii'' is a nonmotile, nonsporeforming, rod-shaped bacterium which can cause dysentery in humans through fecal-oral contamination. ''S. boydii'' is the most genetically divergent species of the genus ''Shigella''. There are 19 known serotypes of ''Shigella boydii''. ''S. boydii'' is restricted to the Indian subcontinent. The species is named after the American bacteriologist Mark Frederick Boyd. Sequenced genomes *''S. boydii'' strain BS512 (serotype 18; group 1) has one chromosome and five plasmids. References External links''Shigella boydii'' Genome Project Page— by Entrez *Type strain of ''Shigella boydii'' at Bac''Dive'' - the Bacterial Diversity Metadatabase Category:Enterobacteriaceae Category:Waterborne diseases Category:Bacteria described in 1949 {{Enterobacterales-stub ...
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Shigella Dysenteriae
''Shigella dysenteriae'' is a species of the rod-shaped bacterial genus ''Shigella''. ''Shigella'' species can cause shigellosis (bacillary dysentery). Shigellae are Gram-negative, non-spore-forming, facultatively anaerobic, nonmotile bacteria. ''S. dysenteriae'' has the ability to invade and replicate in various species of epithelial cells and enterocytes. Epidemiology Shigella infections may be contracted by a lack of monitoring of water and food quality, unsanitary cooking conditions and improper hygiene practices. ''S. dysenteriae'' spreads through contaminated water and food, causes minor dysentery because of its Shiga toxin, but other species may also be dysentery agents. ''S. dysenteriae'' releases an exotoxin that compromises the gut and central nervous system. If acting as an enterotoxin, diarrhea will occur. When acting as a neurotoxin, severe cases of shigellosis are developed, inducing comas and meningismus. Contamination is often caused by bacteria on unwashed hands ...
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Kiyoshi Shiga
was a Japanese physician and bacteriologist. He had a well-rounded education and career that lead to many scientific discoveries. In 1897, Shiga was credited with the discovery and identification of the ''Shigella'' ''dysenteriae'' microorganism which causes dysentery, and the Shiga toxin which is produced by the bacteria. He conducted research on other diseases such as tuberculosis and trypanosomiasis, and made many advancements in bacteriology and immunology. Personal life Shiga was born in Sendai, Miyagi Prefecture. His original surname was Satō, but he changed it to his mother's maiden name, Shiga, after being brought up by his maternal family. Shiga was raised during Japan's Industrial age and restoration. The changing times put financial troubles on his family. In 1900, Kiyoshi Shiga married Ichiko Shiga and in the following years had eight children. He faced many family hardships. Shiga lost his wife in 1944 to stomach cancer, his eldest son to turbulent seas during a voya ...
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Dysentery
Dysentery () is a type of gastroenteritis that results in diarrhea with blood. Other symptoms may include fever, abdominal pain, and a feeling of incomplete defecation. Complications may include dehydration. The cause of dysentery is usually the bacteria ''Shigella'', in which case it is known as shigellosis, or the amoeba ''Entamoeba histolytica''. Other causes may include certain chemicals, other bacteria, other protozoa, or parasitic worms. It may spread between people. Risk factors include contamination of food and water with feces due to poor sanitation. The underlying mechanism involves inflammation of the intestine, especially of the colon. Efforts to prevent dysentery include hand washing and food safety measures while traveling in areas of high risk. While the condition generally resolves on its own within a week, drinking sufficient fluids such as oral rehydration solution is important. Antibiotics such as azithromycin may be used to treat cases associated with trave ...
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Escherichia Coli
''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escherichia'' that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most ''E. coli'' strains are harmless, but some serotypes (EPEC, ETEC etc.) can cause serious food poisoning in their hosts, and are occasionally responsible for food contamination incidents that prompt product recalls. The harmless strains are part of the normal microbiota of the gut, and can benefit their hosts by producing vitamin K2, (which helps blood to clot) and preventing colonisation of the intestine with pathogenic bacteria, having a mutalistic relationship. ''E. coli'' is expelled into the environment within fecal matter. The bacterium grows massively in fresh fecal matter under aerobic conditions for 3 days, but its numbers decline slowly ...
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Verotoxin
Shiga toxins are a family of related toxins with two major groups, Stx1 and Stx2, expressed by genes considered to be part of the genome of lambdoid prophages. The toxins are named after Kiyoshi Shiga, who first described the bacterial origin of dysentery caused by ''Shigella dysenteriae''. Shiga-like toxin (SLT) is a historical term for similar or identical toxins produced by ''Escherichia coli''. The most common sources for Shiga toxin are the bacteria ''S. dysenteriae'' and some serotypes of ''Escherichia coli'' (STEC), which includes serotypes O157:H7, and O104:H4. Nomenclature Microbiologists use many terms to describe Shiga toxin and differentiate more than one unique form. Many of these terms are used interchangeably. # Shiga toxin type 1 and type 2 (Stx-1 and 2) are the Shiga toxins produced by some'' E. coli'' strains. Stx-1 is identical to Stx of ''Shigella spp.'' or differs by only one amino acid. Stx-2 shares 56% sequence identity with Stx-1. # Cytotoxins – a ...
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Shiga Toxin
Shiga toxins are a family of related toxins with two major groups, Stx1 and Stx2, expressed by genes considered to be part of the genome of lambdoid prophages. The toxins are named after Kiyoshi Shiga, who first described the bacterial origin of dysentery caused by ''Shigella dysenteriae''. Shiga-like toxin (SLT) is a historical term for similar or identical toxins produced by ''Escherichia coli''. The most common sources for Shiga toxin are the bacteria ''S. dysenteriae'' and some serotypes of ''Escherichia coli'' (STEC), which includes serotypes O157:H7, and O104:H4. Nomenclature Microbiologists use many terms to describe Shiga toxin and differentiate more than one unique form. Many of these terms are used interchangeably. # Shiga toxin type 1 and type 2 (Stx-1 and 2) are the Shiga toxins produced by some'' E. coli'' strains. Stx-1 is identical to Stx of ''Shigella spp.'' or differs by only one amino acid. Stx-2 shares 56% sequence identity with Stx-1. # Cytotoxins – a ...
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Diarrhea
Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behaviour. This can progress to decreased urination, loss of skin color, a fast heart rate, and a decrease in responsiveness as it becomes more severe. Loose but non-watery stools in babies who are exclusively breastfed, however, are normal. The most common cause is an infection of the intestines due to either a virus, bacterium, or parasite—a condition also known as gastroenteritis. These infections are often acquired from food or water that has been contaminated by feces, or directly from another person who is infected. The three types of diarrhea are: short duration watery diarrhea, short duration bloody diarrhea, and persistent diarrhea (lasting more than two weeks, which c ...
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Fecal–oral Route
The fecal–oral route (also called the oral–fecal route or orofecal route) describes a particular route of transmission of a disease wherein pathogens in fecal particles pass from one person to the mouth of another person. Main causes of fecal–oral disease transmission include lack of adequate sanitation (leading to open defecation), and poor hygiene practices. If soil or water bodies are polluted with fecal material, humans can be infected with waterborne diseases or soil-transmitted diseases. Fecal contamination of food is another form of fecal-oral transmission. Washing hands properly after changing a baby's diaper or after performing anal hygiene can prevent foodborne illness from spreading. The common factors in the fecal-oral route can be summarized as five Fs: fingers, flies, fields, fluids, and food. Diseases caused by fecal-oral transmission include diarrhea, typhoid, cholera, polio and hepatitis. Background School children during a CLTS triggering event in West Ben ...
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Enterotoxin
An enterotoxin is a protein exotoxin released by a microorganism that targets the intestines. Enterotoxins are chromosomally encoded or plasmid encoded exotoxins that are produced and secreted from several bacterial organisms. They are heat labile (>60⁰), and are of low molecular weight and water-soluble. Enterotoxins are frequently cytotoxic and kill cells by altering the apical membrane permeability of the mucosal (epithelial) cells of the intestinal wall. They are mostly pore-forming toxins (mostly chloride pores), secreted by bacteria, that assemble to form pores in cell membranes. This causes the cells to die. Clinical significance Enterotoxins have a particularly marked effect upon the gastrointestinal tract, causing traveler's diarrhea and food poisoning. The action of enterotoxins leads to increased chloride ion permeability of the apical membrane of intestinal mucosal cells. These membrane pores are activated either by increased cAMP or by increased calcium ion concent ...
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Escherichia
''Escherichia'' is a genus of Gram-negative, non-spore-forming, facultatively anaerobic, rod-shaped bacteria from the family Enterobacteriaceae. In those species which are inhabitants of the gastrointestinal tracts of warm-blooded animals, ''Escherichia'' species provide a portion of the microbially derived vitamin K for their host. A number of the species of ''Escherichia'' are pathogenic. The genus is named after Theodor Escherich, the discoverer of ''Escherichia coli''. ''Escherichia'' are facultative aerobes, with both aerobic and anaerobic growth, and an optimum temperature of 37 °C. ''Escherichia'' are usually motile by flagella, produce gas from fermentable carbohydrates, and do not decarboxylate lysine or hydrolyze arginine. Species include ''E. albertii'', ''E. fergusonii'', ''E. hermannii'', ''E. senegalensis'', ''E. marmotae'' and most notably, the model organism and clinically relevant ''E. coli''. ''Shimwellia blattae'' was formerly classified in this genus. Pathogen ...
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Enterohemorrhagic Escherichia Coli
Shigatoxigenic ''Escherichia coli'' (STEC) and verotoxigenic ''E. coli'' (VTEC) are strains of the bacterium ''Escherichia coli'' that produce either Shiga toxin or Shiga-like toxin (verotoxin). Only a minority of the strains cause illness in humans. The ones that do are collectively known as enterohemorrhagic ''E. coli'' (EHEC) and are major causes of foodborne illness. When infecting humans, they often cause gastroenteritis, enterocolitis, and bloody diarrhea (hence the name "enterohemorrhagic") and sometimes cause a severe complication called hemolytic-uremic syndrome (HUS). The group and its subgroups are known by various names. They are distinguished from other strains of intestinal pathogenic ''E. coli'' including enterotoxigenic ''E. coli'' (ETEC), enteropathogenic ''E. coli'' (EPEC), enteroinvasive ''E. coli'' (EIEC), enteroaggregative ''E. coli'' (EAEC), and diffusely adherent ''E. coli'' (DAEC). Two sentences were taken from this source verbatim. Background The best ...
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