HiCrome™ MacConkey-Sorbitol Agar (MacConkey-Sorbitol Agar, HiCrome)

[所属分类:培养基配方] [发布时间:2021-4-8] [发布人: ] [阅读次数:] [返回]

HiCrome™ MacConkey-Sorbitol Agar

(MacConkey-Sorbitol Agar, HiCrome)

培养基配方

Composition per liter:
Casein enzymic hydrolysate.......................................................17.0g
Agar............................................................................................13.5g
Sorbitol .......................................................................................10.0g
NaCl..............................................................................................5.0g
Proteose peptone...........................................................................3.0g
Bile salts mixture..........................................................................1.5g
5-Bromo-4-chloro-3-indolyl-β- D -glucuronide
sodium salt..............................................................................0.1g
Neutral Red.................................................................................0.03g
Crystal Violet............................................................................0.001g
pH 7.1 ± 0.3 at 25°C
Source: This medium is available as a premixed powder from HiMedia.

Preparation of Medium:  Add components to distilled/deionized water and bring volume to 1.0L. Mix thoroughly. Gently heat while stirring and bring to boiling. Mix to completely dissolve components. Do not autoclave. Cool to 50°C. Pour into sterile Petri dishes. 

Use: For the direct isolation and differentiation of E. coli O157:H7 strains from foodstuffs. Recommended for selective isolation of Escherichia coli O157:H7 from food and animal feeds. The medium contains sorbitol instead of lactose. Enteropathogenic strains of Escherichia coli O157:H7 ferment lactose but do not ferment sorbitol and hence produce colorless colonies. Sorbitol fermenting strains of Escherichia coli produce pink-red colonies. The red color is due to pro- duction of acid from sorbitol, absorption of Neutral Red and a subse- quent color change of the dye when the pH of the medium falls below 6.8. The chromogenic indicator is added to detect the presence of an enzyme β- D -glucuronidase. Strains of Escherichia coli possessing β- D - glucuronidase appear as blue colored colonies on the medium. Enteropathogenic strains of Escherichia coli O157 do not possess β- D - glucuronidase activity and thus produce colorless colonies. Escherichia coli fermenting sorbitol and possessing β- D -glucuronidase activity produce purple colored colonies. Most of the Gram-positive organisms are inhibited by Crystal Violet and bile salts.