What is the function of MacConkey agar?

What is the function 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 does MacConkey agar contain?

[2] MacConkey agar contains the essential nutrients required for microorganism growth. Additional key components include crystal violet dye, bile salts, lactose, and neutral red (a pH indicator). The lactose in the agar is a source of fermentation.

What is the use of blood agar?

The primary purpose of Blood agar is for the cultivation and isolation of fastidious organisms like Neisseria and Streptococcus. It can also be used for the differentiation of the bacteria-based type of hemolysis (α-, β- or γ-hemolytic) they produce on the agar.

How do you perform a MacConkey agar test?

Preparation of MacConkey Agar

1. Suspend 49.53 grams of dehydrated medium in 1000 ml of distilled water.
2. Heat to boiling to dissolve the medium completely.
3. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
4. Cool to 45°C -50°C.
5. Mix well before pouring into sterile Petri plates.

What are the constituents of MacConkey agar media?

MacConkey agar media includes various constituents like bile salt, lactose and neutral red, which serve as the indicator system. It helps us to study and identify the growth pattern of the bacterial isolates based on the bile salt precipitation, lactose fermentation and formation of acid.

Why are lactose and lactose added to MacConkey agar?

Peptones are added to MacConkey agar to offer nitrogenous compounds and amino acids. To maintain the osmotic equilibrium, a sodium chloride is added. For carbon energy source, lactose is added in the medium. To inhibit the growth of gram positive organisms, bile salts and crystal violet are added.

Is it necessary to do confirmation tests on MacConkey agar?

It is necessary to subculture and carry out confirmation tests for final identification. Some strains may be encountered that grow poorly or fail to grow on this medium. Incubation of MacConkey Agar plates under increased CO2 has been reported to reduce growth and recovery of a number of strains of Gram-negative bacilli.

Which is the best pH indicator for MacConkey agar?

Sodium chloride maintains the osmotic balance in the medium. Neutral red is a pH indicator that turns red at a pH below 6.8 and is colorless at any pH greater than 6.8. Agar is the solidifying agent. MacConkey agar is used for the isolation of gram-negative enteric bacteria.