MacConkey HiVeg™ Broth (Double Strength) w/ Neutral Red

Principle And Interpretation

MacConkey HiVeg Broth (Double strength) w/ Neutral Red is a modification of MacConkey Broth (Double strength) w/ Neutral Red. It is prepared by replacing animal based peptones with veg peptones and it is free from BSE/TSE risk. MacConkey Broth is widely used as a differential medium for detection and enumeration of coliforms from a wide variety of clinical, food and water samples. Identification is based on colour change of the medium due to the presence of the indicator neutral red (1, 2).

HiVeg peptone provides necessary nitrogen source. Lactose serves as the fermentable carbohydrate source. Sodium chloride maintains the osmotic balance of the cells. The selective action of these media is attributed to the presence of synthetic detergent, which is inhibitory to most species of gram-positive bacteria. Gram-negative bacteria usually grow well on these media and are differentiated by their ability to ferment lactose. The colour change of the medium shown by lactose-fermenters is due to production of acid from lactose and a subsequent colour change of the indicator dye when the pH of the media falls below 6.8. Lactose non-fermenting strains, such as Shigella and Salmonella do not alter the appearance of the media.

MacConkey HiVeg Broth (Double Strength) w/ Neutral Red is recommended for the primary isolation of coliforms form large samples such as water and wastewater. The medium turns pink in case of lactose fermentors and yellow in case of lactose- non-fermenters, due to neutral red. The medium has same composition in double strength to that of MacConkey Broth (M007), which contains neutral red as an indicator and is considered as a standard medium for the primary isolation as well as presumptive identification of coliform-aerogenes group of organisms in food and water.