Endo agar

Endo Agar

Endo Agar plate showing bacterial growth

Endo Agar is a selective and differential culture medium commonly used in microbiology laboratories for the isolation and identification of Gram-negative bacteria. It was first developed by Dr. Masanori Endo in 1957 and has since become a widely used medium due to its effectiveness in distinguishing between different types of bacteria.

Composition

The composition of Endo Agar includes:

• Peptone: Provides a source of nitrogen and amino acids for bacterial growth.
• Lactose: A fermentable carbohydrate that allows for the differentiation of lactose-fermenting and non-lactose-fermenting bacteria.
• Sodium sulfite: Acts as a reducing agent to inhibit the growth of Gram-positive bacteria.
• Ferric ammonium citrate: Serves as an indicator for the detection of hydrogen sulfide production.
• Agar: Solidifying agent that provides a solid surface for bacterial growth.

Selectivity

Endo Agar is selective for Gram-negative bacteria due to the presence of sodium sulfite, which inhibits the growth of Gram-positive bacteria. This selective property allows for the isolation of target bacteria from mixed cultures.

Differential Properties

Endo Agar is also a differential medium, meaning it can differentiate between different types of bacteria based on their ability to ferment lactose. Lactose-fermenting bacteria produce acid during fermentation, which causes the colonies to appear pink or red on the agar. Non-lactose-fermenting bacteria, on the other hand, do not produce acid and appear colorless or pale on the agar.

Hydrogen Sulfide Production

Endo Agar can also detect the production of hydrogen sulfide by bacteria. When bacteria produce hydrogen sulfide, it reacts with ferric ammonium citrate in the medium, resulting in the formation of black colonies or a black precipitate.

Uses

Endo Agar is commonly used in clinical laboratories for the isolation and identification of enteric bacteria, such as Escherichia coli and Salmonella. It is particularly useful in the detection of fecal contamination in food and water samples, as well as in the diagnosis of gastrointestinal infections.

Categories

Endo Agar falls under the following categories:

• Microbiology
• Culture media
• Bacteriology
• Laboratory techniques

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