Rapid HiColiform™ HiVeg™ Broth

Principle And Interpretation

Rapid HiColiform HiVeg™ Broth is prepared by completely replacing animal based peptones with veg peptones. It is a modification of Rapid HiColiform Broth which is a modification of LMX Broth described by Manafi and Kneifel (2). This medium is useful for the detection and confirmation of Escherichia coli and total coliforms in water samples on the basis of chromogenic and fluorognic substrates (1-6).

The fluorogenic substrate is split by enzyme β-D-glucuronidase specifically found in Escherichia coli. The reaction is indicated by the development of a blue fluorescence under UV light. The presence of total coliforms is indicated by blue-green colouration due to the cleavage of the chromogenic substrate. IPTG amplifies enzyme synthesis and increases the activity of β-D-galactosidase. To confirm presence of E. coli overlay the medium with Kovacs reagent. The layer turns red within 2 minutes in case of positive reaction.

HiVeg Special Peptone, (rich in tryptophan content), provides essential growth nutrients and is useful for the simultaneous detection of indole production. Sorbitol provides the carbon source. The phosphate salts provide buffering action for rapid growth of coliforms. Sodium lauryl sulphate makes the medium selective by inhibiting accompanying microflora, especially the gram-positive organisms.