M-Chromogenic Coliform Broth in Tubes

M-Chromogenic Coliform Broth is a differential medium for the detection and enumeration of coliforms and E. coli in water samples. The combined action of peptone, pyruvate, and sorbitol allows rapid colony growth in this phosphate-buffered medium, which also permits simple recovery of sublethal thermally injured coliforms. Sodium chloride provides the correct osmotic environment for microbial growth.Tergitol^™ 7 inhibits the growth of Gram-positive and some Gram-negative bacteria without affecting the coliforms. Cefsulodin and Vancomycin act against Pseudomonas and Gram-negative, oxidase-positive bacteria, Enterococci, and other Gram-positive bacteria thereby enhancing the selectivity. The colonial differentiation is due to the chromogenic mixture composed of two enzyme substrates: 6-chloro-3-indoxyl-ß-D-galacto-pyranoside (Salmon-GAL) and 5-bromo-4-chloro-3-indoxyl-ß-D-glucuronide. (X-Glucuronide). ß-D-galactosidase, a characteristic enzyme found in coliforms, cleaves the first substrate and gives a mauve to light lilac color to the coliform colonies. ß-D-glucuronidase, a characteristic enzyme of E. coli, cleaves the second chromogenic substrate and turns the colonies of these bacteria blue to purple.E. coli colonies are confirmed by including a small amount of tryptophan in the medium and coating the blue-violet colonies with a drop of Kovacs Reagent. The color change of the reagent to cherry-red in a few seconds confirms the production of indole and thereby, the presence of E. coli. When the Chromogenic Agar for Coliform is used with the membrane filter method, the color and growth of the colonies can be modified by the characteristics of the membrane filter. It is advisable to perform validation of the membrane filter type used.

M-Chromogenic Coliform Broth in Tubes is a selective and differential medium for the detection and enumeration of coliforms and E. coli in water samples by membrane filtration technique.

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