O-F Base Medium

O-F Base Medium

SKU: KM0143 Category: Tag:

O-F Medium is used for the determination of oxidative and fermentative metabolism of carbohydrates by Gram-negative bacilli (1).
This is on the basis of the acid reaction in either the open or closed system that has been covered with sterile paraffin oil.
Changes in the covered agar are considered to be due to true fermentation, while changes in the open tubes are due to the oxidative utilization of the carbohydrate present.
O-F Base Medium requires the addition of the specific carbohydrate being investigated.
The enzymatic digest of casein provides the required nitrogen, carbon and vitamins in the media.
Sodium chloride maintains the osmotic balance.
Di-potassium hydrogen phosphate acts as a buffer and bromothymol blue is a pH indicator.
The agar is a solidifying agent.

(1) Hugh, R. and Leifson, E.J. 1953. Bacteriol. 66:24-26.

Additional Information


Shelf Life (days)

Storage Temp (°C)

Dehydrated Medium Appearance

Dehydrated Medium Colour

Prepared Medium Colour

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Prepared PH

Product Description

Organisms Ref. No Result
Escherichia coli NCTC 12241 Growth, fermentation reaction
Escherichia coli NCTC 12241 Growth, oxidative reaction
C. perfringens NCTC 8237 Growth, oxidative reaction

Recommended incubation: Aerobically at 37 ± 1°C for 24 ± 2 hours

Carbohydrate utilisation Open tube (No overlay) Closed (Oil overlay)
Oxidation Positive
Medium turns yellow
Medium remains green
Fermentation Positive
Medium turns yellow
Medium turns yellow
Medium remains green
Medium remains green