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Salmonella species: red colonies, some with black centers. The agar itself will turn red due to the presence of Salmonella type colonies. Shigella species: red colonies. Coliforms: yellow to orange colonies. Pseudomonas aeruginosa: pink, flat, rough colonies. This type of colony can be easily mistaken for Salmonella due to the color similarities.
XLT Agar (Xylose Lysine Tergitol-4) is a selective culture medium for the isolation and identification of salmonellae from food and environmental samples. It is similar to XLD agar; however, the agar is supplemented with the surfactant, Tergitol 4, which causes inhibition of Proteus spp. and other non-Salmonellae. [1]
Shigellosis (Historically the disease usually referred to as Dysentery) is an infection of the intestines caused by Shigella bacteria. [1] [3] 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. [1]
Shigella infections may be contracted by a lack of monitoring of water and food quality, unsanitary cooking conditions and improper hygiene practices. [6] S. dysenteriae spreads through contaminated water and food, causes minor dysentery because of its Shiga toxin, but other species may also be dysentery agents. [7]
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 ...
Hektoen enteric agar (HEK, HE or HEA) is a selective and differential agar [1] primarily used to recover Salmonella and Shigella from patient specimens. HEA contains indicators of lactose fermentation and hydrogen sulfide production; as well as inhibitors to prevent the growth of Gram-positive bacteria.
Salmonella species can be found in the digestive tracts of humans and animals, especially reptiles. Salmonella on the skin of reptiles or amphibians can be passed to people who handle the animals. [39] Food and water can also be contaminated with the bacteria if they come in contact with the feces of infected people or animals. [40]
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 ]