What are the morphological characteristics of Salmonella on MacConkey agar?

What are the morphological characteristics of Salmonella on MacConkey agar?

CULTURE CHARACTERISTICS OF SALMONELLA TYPHI (S. TYPHI)

Cultural Characteristics	Nutrient Agar Medium (NAM)	MacConkey Agar medium
Elevation	Low Convex	Low Convex
Surface	Smooth	Smooth
Color	Greyish white	Colorless
Structure	Translucent	Transparent

What is the colony morphology of Salmonella?

Salmonella colony appear as low convex, pale green translucent colonies 1-3 mm is diameter. Lactose fermenting bacteria produce the purple colonies.

Can Salmonella grow on MacConkey agar?

Principle of MacConkey Agar Sodium chloride maintains the osmotic balance in the medium. Lactose fermenting strains grow as red or pink. Non-lactose fermenting bacteria such as Salmonella, Proteus, Pseudomonas aeruginosa and Shigella cannot utilize lactose, and will use peptone instead.

What should the colonies of Salmonella spp look like on a MacConkey agar plate?

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. Yersinia enterocolitica may appear as small, non-lactose fermenting colonies after incubation at room temperature.

What do Salmonella colonies look like?

Typical Salmonella appear as blue-green to blue colonies with black centers. Many Salmonella cultures have large glossy black centers or may appear as almost completely black colonies.

What are the characteristics of Salmonella?

Salmonellosis is a disease caused by the bacteria Salmonella. It is usually characterized by acute onset of fever, abdominal pain, diarrhoea, nausea and sometimes vomiting. The onset of disease symptoms occurs 6–72 hours (usually 12–36 hours) after ingestion of Salmonella, and illness lasts 2–7 days.

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.

What does Salmonella look like on an agar plate?

Salmonella species: red colonies, some with black centers. The agar itself will turn red due to the presence of Salmonella type colonies.

What Agar does Salmonella grow on?

Xylose Lysine Deoxycholate agar (XLD agar) is a selective growth medium used in the isolation of Salmonella and Shigella species from clinical samples and from food.

Does Bacillus grow on MacConkey Agar?

Bacillus cereus has a large, smooth, pink colonies with mousy smell on MacConkey’s agar. Lactose non-fermenter colonies on the MacConkey’s agar and central black, small size colonies with smooth to rough in appearance on the Salmonella-Shigella agar were identified as Salmonella spp.

How does E coli look on blood agar?

An isolate from urine can be quickly identified as E. coli by its hemolysis on blood agar, typical colonial morphology with an iridescent “sheen” on differential media such as EMB agar, and a positive spot indole test result.

What is the indicator in MacConkey Agar?

Key components of the MacConkey medium include crystal violet dye, bile salts, lactose, and neutral red (pH indicator). Crystal violet dye and bile salts halt the growth of gram-positive bacteria. This allows only gram-negative species to form colonies on MAC agar.

What are the expected colony characteristics of MacConkey agar?

Expected Colony characteristics in MacConkey Agar Lactose-fermenting organisms grow as pink to brick red colonies with or without a zone of precipitated bile. Non-lactose fermenting organisms grow as colorless or clear colonies

How does Salmonella typhi grow in blood agar medium?

In Blood Agar medium, the Salmonella typhi shows gamma hemolysis i.e. no hemolysis occur on blood agar medium, the colonies are grayish white and grows well. CULTURE OF SALMONELLA TYPHI ON BLOOD AGAR MEDIUM

Why are the colonies of Salmonella typhi black?

In Deoxycholate Citrate Agar medium, the colonies of Salmonella typhi are colorless due to Non-Lactose Fermentation (NLF). In Salmonella Shigella Agar medium, the colonies of Salmonella typhi are Colorless with black center, due to the production of H2S (Hydrogen sulfide).

How to tell the size of a CLED agar colony?

Colonies of Gram-positive cocci appear yellow but smaller in size as compared to Gram-negative ones. QC of CLED agar should be done by performing sterility testing and performance testing.