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Salmonella species lead predominantly host-associated lifestyles, but the bacteria were found to be able to persist in a bathroom setting for weeks following contamination, and are frequently isolated from water sources, which act as bacterial reservoirs and may help to facilitate transmission between hosts. [31]
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 ...
Shigella flexneri is a rod shaped, nonflagellar bacterium that relies on actin-based motility. It produces the protein actin in a swift and continuous fashion to propel itself forward within and between the host's cells. [4] This bacterium is gram-negative, non-spore forming Shigella from serogroup B. There are 6 serotypes within this serogroup.
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.
Unlike other bacteria, Shigella is not destroyed by the gastric acid in the stomach. As a result, it takes only 10 to 200 cells to cause an infection. [ 13 ] This infectious dose is several orders of magnitude smaller than that of other species of bacteria (e.g., cholera , caused by the bacterium Vibrio cholerae , has an infectious dose between ...
The increase in pH then causes color change in the bromothymol blue indicator, turning it blue. Under neutral conditions the medium remains a green color. The color change to blue is useful because growth on Simmons' citrate agar is often limited and would be hard to observe if it were not for the color change.
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.
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.