AM13-111500 - Broth, MacConkey, 500g

MacConkey Broth, 500g

Use: MacConkey Broth is used to detect the presence of gram-negative, lactose-fermenting enteric bacteria in samples of water, milk and other materials of sanitary importance.

Description: MacConkey Broth is a formulation recommended by the World Health Organization and is a modification of a formula developed by MacConkey. The broth medium is used for the presumptive determination of the presence of coliforms in water, milk and other sanitary materials. Presence of lactose- fermenting bacteria is detected by the change of color of the medium (from purple to yellow) after inoculation and incubation. The original formula used litmus as an indicator of acid reaction. Later investigations utilized neutral red as an indicator but were found to be inhibitory towards Escherichia coli. Bromcresol purple is now used since it is less inhibitory and gives distinct acid reactions. MacConkey Broth was formulated to support the growth of enteric bacteria and detect the presence of lactose fermenting bacteria. Bile (Oxgall) is incorporated into to the medium to inhibit gram-positive bacteria. Lactose is the fermentable carbohydrate and the fermentation reaction which gives an acid reaction is detected by the change in color of bromcresol purple from purple to yellow.

Formula* per Liter:

Pancreatic Digest of Gelatin: 20.0g
Lactose:10.0g
Oxgall: 5.0g
Bromcresol Purple: 0.015g
Final pH: 7.3 ± 0.2 at 25.0°C

* Grams per liter may be adj. or formula supplemented to obtain desired performance.