Coliform Agar, Chromocult ® (Chromocult Coliform Agar)

[所属分类:培养基配方] [发布时间:2020-5-21] [发布人:] [阅读次数:] [返回]

山东拓普生物工程有限公司

Shandong Tuopu Biol-Engineering Co.,Ltd

Coliform Agar, Chromocult ®
(Chromocult Coliform Agar)

培养基配方
Composition per liter:
Agar .......................................................................10.0g
NaCl.........................................................................5.0g
Peptone......................................................................3.0g
Na2HPO4 .....................................................................2.7g
NaH2PO4 .....................................................................2.2g
Tryptophan...................................................................1.0g
Na-pyruvate .................................................................1.0g
Chromogenic mixture..........................................................0.4g
Tergitol 7..................................................................0.15g
pH 7.0 ± 0.2 at 25°C
Source: This medium is available from Merck.
Preparation of Medium: Add components to distilled/deionized
water and bring volume to 1.0L. Mix well and warm gently until dis-
solved. Autoclave for 15 min at 15 psi pressure–121°C. Pour into ster-
ile Petri dishes. Some turbidity may occur, but this does not effect the
performance.
Use: For the detection of E. coli and coliform bacteria in foods. The
interaction of selected peptones, pyruvate, sorbitol, and phosphate buf-
fer guarantees rapid colony growth, even for sublethally injured coli-
forms. The growth of Gram-positive bacteria as well as some Gram-
negative bacteria is largely inhibited by the content of Tergitol 7 which
has no negative effect on the growth of the coliform bacteria. A com-
bination of two chromogenic substrates allows for the simultaneous
detection of total coliforms and E. coli.The characteristic enzyme for
coliforms, β- D -galactosidase, cleaves the Salmon-GAL substrate and
causes a salmon to red color of the coliform colonies. The substrate X-
glucuronide is used for the identification of β- D -glucuronidase, which
is characteristic for E. coli. E. coli cleaves both Salmon-GAL and X-
glucuronide, so that positive colonies take on a dark-blue to violet
color. These are easily distinguished from other coliform colonies
which have a salmon to red color. As part of an additional confirmation
of E. coli, the inclusion of tryptophan improves the indole reaction,
thereby increasing detection reliability when it is used in combination
with the Salmon-GAL and X-glucuronide reaction.