HiCrome™ MacConkey-Sorbitol Agar with Tellurite-Cefixime Supplement (MacConkey-Sorbitol Agar with Tellurite-Cefixime Supplement)

[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
with Tellurite-Cefixime Supplement
(MacConkey-Sorbitol Agar with

Tellurite-Cefixime Supplement)

培养基配方

Composition per 1004.0mL:
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
Tellurite-cefixime supplement...................................................4.0mL
pH 7.1 ± 0.3 at 25°C
Source: This medium, without tellurite-cefixime supplement, is available as a premixed powder from HiMedia.
Tellurite-Cefixime Supplement:
Composition per 4.0mL :
K 2 TeO 3 .......................................................................................5.0mg
Cefixime.....................................................................................0.1mg
Preparation of Tellurite-Cefixime Supplement: Add components to 4.0mL of distilled/deionized water. Mix thoroughly. Filter sterilize.
Caution: Potassium tellurite is toxic.
Source: This medium is available from Fluka, Sigma-Aldrich. Tellurite-cefixime supplement is available from Oxoid Unipath.
Preparation of Medium:  Add components, except tellurite-cefixi- me supplement, 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. Add 4.0mL sterile tellurite-cefixime supplement. Mix thoroughly. 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 feeding stuffs. 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 production of acid from sorbitol, absorption of Neutral Red and a sub- sequent 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. Entero- pathogenic strains of Escherichia coli O157 do not possess β- D - glucuronidase activity and thus produce colorless colonies. Escheri- chia coli fermenting sorbitol and possessing β- D -glucuronidase activ- ity produce purple colored colonies. Most of the Gram-positive organ- isms are inhibited by Crystal Violet and bile salts. Addition of tellurite- cefixime supplement makes the medium selective. Potassium tellurite selects the serogroups O157 from other E. coli serogroups and inhibits Aeromonas species and Providencia species. Cefixime inhibits Proteus species.