For the detection enumeration of coliform bacteria. MacCONKEY BROTH is used for the selective enrichment and enumeration of coliform bacteria. It conforms to harmonized USP/EP/JP requirements.1,2,3 MacConkey Broth is a modification of the original Bile salt broth recommended by MacConkey, containing 0.5% sodium taurocholate and litmus as an indicator.4MacConkey suggested further variations of this formula using neutral red indicator instead of litmus.5,6Childs and Allen demonstrated the inhibitory effect of neutral red and substituted the less inhibitory Bromcresol purple.7 Pancreatic digest of Gelatin provides necessary nitrogen source. Lactose is the carbohydrate for Gram-negative lactose-fermenting bacilli. Sodium chloride maintains the osmotic balance of the cells. Dehydrated Ox bile inhibit the growth of Gram-positive organisms. Gram-negative bacteria usually grow well on this media and are differentiated by their ability to ferment lactose. Lactose-fermenting organisms grow very well in MacConkey Broth and produce acid, causing the medium to turn yellow. Gas is also produced, which collects in the Durham tubes. Non-fermenting organisms produce good growth but will not produce acid or gas. Inoculate 10ml. MacConkey Broth (TMH 109) medium with a small number (not more than 100 cfu) of the appropriate microorganism and incubate at 35±2°C for 18-24 hours. Subculture on a plate of MacConkey Agar (TMH 110) and incubate at 35±2°C for 18-24 hours.