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Chromogenic Enterobacter sakazakii Agar, DFI Formulation

[所屬分類:培養基配方] [發布時間:2021-11-12] [發布人:網站管理員2] [閱讀次數:] [返回]

Chromogenic Enterobacter sakazakii

Agar, DFI Formulation

山東(dong)拓普生物工(gong)程有限(xian)公司培(pei)養(yang)基配方 //ljxinglong.com

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 dis

tilled/deionized water 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 En

terobacter sakazakii from infant formula and other

food samples. The enzyme α-glucosidase, present in

E. sakazakii, hydrolyzes the substrate 5-bromo-4-

chloro-3-indolyl-α,D-glucopyranoside, thus produc

ing blue-green colonies on this pale yellow medium.

Proteus vulgaris is also weakly α-glucosidase posi

tive and could grow to give colonies of a similar col

or to E. sakazakii. However, on this medium, Proteus

spp. grow as grey colonies: they produce hydrogen

sulphide in the presence of ferric ions forming fer

rous sulphide. Deoxycholate inhibits the growth of

most Gram-positive organisms.