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Shigella is a genus of bacteria that is Gram negative, facultatively anaerobic, non–spore-forming, nonmotile, rod shaped, and is genetically nested within Escherichia. The genus is named after Kiyoshi Shiga, who discovered it in 1897. [1] Shigella causes disease in primates, but not in other mammals; it is the causative agent of human ...
Salmonella is a genus of rod-shaped, (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two known species of Salmonella are Salmonella enterica and Salmonella bongori. S. enterica is the type species and is further divided into six subspecies [2] [3] that include over 2,650 serotypes. [4]
Salmonellosis is a symptomatic infection caused by bacteria of the Salmonella type. [1] It is the most common disease to be known as food poisoning (though the name refers to food-borne illness in general), these are defined as diseases, usually either infectious or toxic in nature, caused by agents that enter the body through the ingestion of food.
Escherichia coli is one of the most important model organisms, and its genetics and biochemistry have been closely studied. Some enterobacteria are important pathogens, e.g. Salmonella, or Shigella e.g. because they produce endotoxins. Endotoxins reside in the cell wall and are released when the cell dies and the cell wall disintegrates.
Since Salmonella typically exhibit phase variation between two motile phenotypes, [3] different "H" antigens may be expressed. Salmonella that can express only one "H" antigen phase consequently have motile and non-motile phenotypes and are termed monophasic, whilst isolates that lack any "H" antigen expression are termed non-motile. [4]
The term is usually restricted to Shigella infections. [2] Shigellosis is caused by one of several types of Shigella bacteria. [3] Three species are associated with bacillary dysentery: Shigella sonnei, Shigella flexneri and Shigella dysenteriae. [4] A study in China indicated that Shigella flexneri 2a was the most common serotype. [5]
Having just one membrane, the gram-positive bacteria are also known as monoderm bacteria, while gram-negative bacteria, having two membranes, are also known as diderm bacteria. It was traditionally thought that the groups represent lineages, i.e., the extra membrane only evolved once, such that gram-negative bacteria are more closely related to ...
It contains two dyes, eosin and methylene blue in the ratio of 6:1. EMB is a differential microbiological media, which inhibits the growth of Gram-positive bacteria and differentiates bacteria that ferment lactose (e.g., E. coli) from those that do not (e.g., Salmonella, Shigella). [2]