What is the colony morphology of Shigella?
Morphology of Shigella: They are short Gram-negative bacilli, 0.5 p x 1-3 p in size, fimbriate, non-motile, non-sporing and non-capsulated.
What Agar does Shigella grow on?
SS Agar
SS Agar (Salmonella Shigella Agar) is a differential selective media used for the isolation of Salmonella and some Shigella species from pathological specimens, and suspected foods. The peptic digest of animal tissue and beef extract provide essential growth nutrients. Lactose is the fermentable carbohydrate.
What medium does Shigella grow?
Salmonella Shigella (SS) Agar is a moderately selective and differential medium for the isolation, cultivation, and differentiation of Salmonella spp. and some strains of Shigella spp. SS Agar is a modification of the Deoxycholate Citrate Agar.
What color are Shigella colonies?
colorless
Result Interpretation on Salmonella Shigella Agar The resulting bacterial colonies will appear colorless with black centers. Shigella do not ferment lactose or produce hydrogen sulfide gas, so the resulting colonies will be colorless.
Can Shigella grow on nutrient agar?
⇒ Special requirements – Shigella dysenteriae have no complex nutritional requirements and readily grow in ordinary media like Nutrient Agar medium (NAM).
How do you identify Shigella?
Infection is diagnosed when a laboratory identifies Shigella in the stool (poop) of an ill person. The test could be a culture that isolates the bacteria or a rapid diagnostic test that detects genetic material of the bacteria.
Does Shigella grow on SS Agar?
On SS Agar, colonies of Salmonella or Shigella are smooth and opaque or colorless. Strains of Salmonella which produce H2S will form black-centered colonies. Lactose-fermenters are pink to rose-red in color and may have a precipitate.
Is Shigella a lactose fermenter?
Shigella species are Gram-negative, nonmotile, rod-shaped, facultative anaerobes that almost universally are unable to produce hydrogen sulfide, do not ferment lactose or show late lactose fermentation, fail to utilize citrate as a sole carbon source, and do not generate gas from carbohydrate fermentation.
What color is Shigella on SS Agar?
On SS Agar, colonies of Salmonella or Shigella are smooth and opaque or colorless. Strains of Salmonella which produce H2S will form black-centered colonies. Lactose-fermenters are pink to rose-red in color and may have a precipitate.
Does Shigella grow on MacConkey agar?
Shigella grows as non-lactose-fermenting colonies on MacConkey agar, although a more selective agar is used for the isolation of Shigella from feces, such as deoxycholate citrate agar and xylose lysine deoxycholate agar. Biochemically, Shigella spp.
Is Shigella a glucose fermenter?
Nonetheless, Shigella species are Gram-negative, facultatively anaerobic, nonsporulating, nonmotile rods in the family Enterobacteriaceae. They do not decarboxylate lysine or ferment lactose within 2 days. They utilize glucose and other carbohydrates, producing acid but not gas.
What is color of Shigella in MacConkey agar?
colourless
Result Interpretation on MacConkey Agar Lactose non-fermenting strains, such as Shigella and Salmonella are colourless and transparent and typically do not alter appearance of the medium.
Can Shigella be cultured?
Because the Shigella are members of the same family as E. coli, most of the culture media and techniques used for growth and maintenance of E. coli work well for the Shigella species.
What sugars does Shigella ferment?
Notice that Shigella dysenteriae (far left) ferments glucose but does not produce gas. *Note – broth tubes can be made containing sugars other than glucose (e.g. lactose and mannitol).
Is Shigella lactose fermenter?
How does Shigella look on MacConkey agar?
Result Interpretation on MacConkey Agar Lactose non-fermenting strains, such as Shigella and Salmonella are colourless and transparent and typically do not alter appearance of the medium.
Is Shigella a Gram positive or Gram-negative?
Shigellae are Gram-negative, nonmotile, facultatively anaerobic, non-spore-forming rods. Shigella are differentiated from the closely related Escherichia coli on the basis of pathogenicity, physiology (failure to ferment lactose or decarboxylate lysine) and serology.
Does Shigella ferment sucrose?
The characteristics of Shigella are summarized as follows: Gram-negative rods; negative for H2S, urease, glucose (gas), motility, lysine decarboxylase, sucrose, adonitol, inositol, lactose (2 days), KCN, malonate, citrate, and salicin; positive for methyl red.
What are the cultural characteristics of Shigella?
Cultural Characteristics of Shigella: They are aerobes and facultative anaerobes, grow best at 37°, pH 7.4 on ordinary media. Colonies are small, about 2 mm in diameter, circular, convex, smooth and transparent; on MacConkey’s agar medium they are pale or colourless except Sh. sonnei which is late lactose fermenter.
How do you identify Shigella colonies on agar?
Shigella colonies are slightly pink and translucent, with or without rough edges. Inoculate suspicious colonies into the following media: glucose broth, TSI agar slant, lysine decarboxylase broth , motility agar, and tryptone.
What is the principle of Salmonella Shigella agar?
Principle of Salmonella Shigella Agar. The inclusion of Bile Salts, Sodium Citrate and Brilliant Green serve to inhibit gram-positive, coliform organisms and inhibit swarming Proteus spp., while allowing Salmonella spp. to grow. Beef Extract, Enzymatic Digest of Casein, and Enzymatic Digest of Animal Tissue provide sources of nitrogen,…
What is the color of Shigella dysenteriae colonies on deoxycholate citrate agar?
In the Deoxycholate Citrate Agar medium, the colonies of Shigella dysenteriae are colorless due to Non-Lactose Fermentation (NLF). In Salmonella Shigella Agar medium, the colonies of Shigella dysenteriae are Colorless.