Microbiological Culture Medium MacConkey Agar tissue culture medium

Purpose: For the selective isolation and cultivation of Salmonella.

Composition (g/L):

Yeast Extract Powder: 3.0

L-Lysine: 5.0

Lactose: 7.5

Sucrose: 7.5

Xylose: 3.5

Sodium Chloride: 5.0

Sodium Thiosulfate: 6.8

Ferric Ammonium Citrate: 0.8

Sodium Deoxycholate: 2.5

Phenol Red: 0.08

Agar: 13.5

pH Value: 7.4 ± 0.2 at 25°C.

Testing Principle:

Yeast extract powder provides vitamins and growth factors for bacterial growth; xylose, lactose, and sucrose serve as fermentable carbon sources. Most Enterobacteriaceae, except Shigella, ferment xylose. Lysine is added to differentiate Salmonella. Salmonellaferments xylose to produce acid. The resulting acidic environment favors the production of decarboxylase by the bacteria. Salmonelladecarboxylates lysine, raising the medium's pH towards alkalinity. However, this shift can be inhibited by the large amount of acid produced from the fermentation of lactose and sucrose by other bacteria. Under alkaline conditions, sodium thiosulfate and ferric ammonium citrate react with hydrogen sulfide produced by Salmonella, causing the colonies to appear black. This reaction is inhibited under acidic conditions. Phenol red acts as a pH indicator. Sodium chloride maintains the osmotic balance of the system. Deoxycholate inhibits the growth of Gram-positive bacteria.

Usage:

Weigh 57.0g of this product, heat and stir to dissolve in 1000ml of purified water. Do not overheat. When cooled to 50°C, pour into sterile Petri dishes. It is ready for use. Autoclaving is not required.

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