Chromogenic Enterobacter sakazakii Agar, DFI Formulation

[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 Enterobacter sakazakii Agar,
DFI Formulation

培养基配方
Composition per liter:
Agar ........................................................................15.0g
Tryptone.....................................................................15.0g
Soya peptone..................................................................5.0g
NaCl..........................................................................5.0g
Ferric ammonium citrate.......................................................1.0g
Sodium deoxycholate...........................................................1.0g
Na2S2O3 ......................................................................1.0g
Chromogen.....................................................................0.1g
pH 7.3 ± 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. Allow
tubes to cool in a slanted position.
Use: For the differentiation and enumeration of Enterobacter saka-
zakii from infant formula and other food samples. The enzyme α-glu-
cosidase, present in E. sakazakii, hydrolyzes the substrate 5-bromo-4-
chloro-3-indolyl-α, D -glucopyranoside, thus producing blue-green col-
onies on this pale yellow medium. Proteus vulgaris is also weakly α-
glucosidase positive and could grow to give colonies of a similar color
to E. sakazakii. However, on this medium, Proteus spp. grow as grey
colonies: they produce hydrogen sulphide in the presence of ferric ions
forming ferrous sulphide. Deoxycholate inhibits the growth of most
Gram-positive organisms.