Chromogenic E. coli/Coliform Medium

[所属分类:培养基配方] [发布时间:2020-4-29] [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

Chromogenic E. coli/Coliform Medium

培养基配方
Composition per liter:
Chromogenic mix ...........................................................20.3g
Agar ......................................................................15.0g
Peptone.....................................................................5.0g
NaCl........................................................................5.0g
Na2HPO4 ....................................................................3.5g
Yeast extract...............................................................3.0g
Lactose.....................................................................2.5g
NaH2PO4 ....................................................................1.5g
Neutral Red................................................................0.03g
pH 6.8 ± 0.2 at 25°C
Preparation of Medium: Add components to distilled/deionized wa-
ter and bring volume to 1.0L. Mix thoroughly. Gently heat and bring to
boiling. Dispense into tubes or flasks. Autoclave for 15 min at 15 psi
pressure–121°C. Pour into sterile Petri dishes or leave in tubes.
Use: For the differentiation between Escherichia coli and other coli-
forms in cultures produced from food samples. Agar base uses two en-
zyme substrates to differentiate between E. coli and other coliforms.
One chromogenic substrate is cleaved by the enzyme glucuronidase
which is specific for E. coli and produced by approximately 97% of
strains. The second chromogenic substrate is cleaved by galactosidase,
an enzyme produced by the majority of coliforms. This results in pur-
ple E. coli colonies, as they are able to cleave both chromogenic sub-
strates and pink coliform colonies as they are only able to cleave the
galactosidase chromogen.