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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.
Three Shigella groups are the major disease-causing species: S. flexneri is the most frequently isolated species worldwide, and accounts for 60% of cases in the developing world; S. sonnei causes 77% of cases in the developed world, compared to only 15% of cases in the developing world; and S. dysenteriae is usually the cause of epidemics of ...
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]
Enterobacteriaceae is a large family of Gram-negative bacteria.It includes over 30 genera and more than 100 species. Its classification above the level of family is still a subject of debate, but one classification places it in the order Enterobacterales of the class Gammaproteobacteria in the phylum Pseudomonadota.
Önöz agar allows more rapid bacteriological diagnosis, as Salmonella and Shigella colonies can be clearly and reliably differentiated from other Enterobacteriaceae. The yields of Salmonella from stool samples obtained, when using this medium, are higher than those obtained with LEIFSON agar or Salmonella–Shigella agar.
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.
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] Organisms that ferment lactose appear dark/black or green often with "nucleated colonies"—colonies with dark centers. [3]
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 ]