What is MacConkey agar used for?

MacConkey Agar (MAC) is a selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose. Bile salts and crystal violet inhibit the growth of Gram positive organisms.

What is MacConkey used to identify?

MacConkey agar is used for the isolation of gram-negative enteric bacteria. It is used in the differentiation of lactose fermenting from lactose non-fermenting gram-negative bacteria. It is used for the isolation of coliforms and intestinal pathogens in water, dairy products and biological specimens.

Is MacConkey agar defined?

Is MacConkey agar a defined or an undefined medium? Provide the reasoning behind your choice and explain why this formulation is desirable. It is undefined due to the pancreatic digests of gelatin and casein, peptic digest of animal tissue, and bile salts in the medium.

What are the characteristics of MacConkey agar?

MacConkey agar contains four key ingredients (lactose, bile salts, crystal violet, and neutral red) that make it a selective and differential media. Bile salts and crystal violet act as selective agents that inhibit the growth of Gram-positive organisms, and proliferate the selective growth of gram-negative bacteria.

What ingredients are in MacConkey agar that make it selective?

The selective ingredients are the bile salts and the dye, crystal violet which inhibit the growth of Gram-positive bacteria. The differential ingredient is lactose. Fermentation of this sugar results in an acidic pH and causes the pH indicator, neutral red, to turn a bright pinky-red color.

Why is MacConkey agar used for E coli?

Sorbitol MacConkey agar is a variant of traditional MacConkey agar used in the detection of E. coli O157:H7. This is important because gut bacteria, such as Escherichia coli, can typically ferment lactose, while important gut pathogens, such as Salmonella enterica and most shigellas are unable to ferment lactose.

How is MacConkey agar selective and differential?

This medium is both selective and differential. The selective ingredients are the bile salts and the dye, crystal violet which inhibit the growth of Gram-positive bacteria. The differential ingredient is lactose.

Which bacteria can grow on MacConkey agar?

Altogether, MacConkey agar only grows gram-negative bacteria, and those bacteria will appear differently based on their lactose fermenting ability as well as the rate of fermentation and the presence of a capsule or not.

Is MacConkey selective or differential?

MacConkey agar is an example of a medium that is both differential and selective. The presence of bile salts, as well as crystal violet, within the media prevent gram-positive organisms from growing.

What are the sugars present in MacConkey agar?

What types of bacteria are inhibited on MacConkey agar?

Uses of MacConkey Agar MacConkey agar is used for the isolation of gram-negative enteric bacteria. It is used in the differentiation of lactose fermenting from lactose non-fermenting gram-negative bacteria. It is used for the isolation of coliforms and intestinal pathogens in water, dairy products and biological specimens.

What foods contain agar agar?

Common Foods Containing Agar-Agar: Agar-agar is commonly used in processed foods such as doughnuts, marmalade & jam, jelly candy, cheese, puddings, gelatin fruit desserts, meat products, bakery fillings and icings, dry and canned soups and ice cream.

What can Gram positive organisms grow on MacConkey agar?

The MacConkey agar can only develop gram negative bacteria. The agar used in MacConkey test contains crystal violet colorant, which is the first colorant used in gram staining. What crystal violet does is it deeply penetrates the cell wall of gram positive bacteria.

Does Proteus swarm on MacConkey agar?

MacConkey Agar, CS (“Controlled Swarming”): MacConkey agar without Crystal Violet or Salt and MacConkey Agar without Salt is used to prevent the swarming of Proteus spp. Sorbitol MacConkey Agar: Sorbitol MacConkey agar is a variant of MacConkey agar, it contains sorbitol instead of lactose as fermentable sugar.