Enterobacteria Enrichment Broth, Mossel

Principle And Interpretation

EE Broth, Mossel, formulated by Mossel et. al.(1-5) is recommended as an enrichment medium for bile tolerant gram-negative bacteria in the biological examination of foods (1), animal feed stuffs (6) and is in accordance with the harmonized method of USP/EP/BP/JP & IP (7-11).

Gelatin peptone and glucose monohydrate allows the growth of most of the members of Enterobacteriaceae. Brilliant green and dehydrated bile, purified are the inhibitory agents for gram-positive bacteria. Phosphates act as a good buffering agent and neutralizes acids produced by lactose fermenters that otherwise would adversely affect the growth of the organism. Lactose negative, anaerogenic lactose-positive or late lactose fermenting Enterobacteriaceae are often missed by the standard Coli-aerogenes test. To overcome this problem, lactose is replaced by glucose in this medium. Phosphates form the buffering system of the medium. The cells damaged while drying or low pH are resuscitated in well-aerated Tryptone Soya Broth (M011) for 2 hours at 25°C prior to enrichment in EE Broth. The resuscitation procedure is recommended for dried foods (4), animal feeds (5) and semi-preserved foods (12). EE Broth is an enrichment broth and a loopful of the enriched sample is then subcultured onto Violet Red Bile Glucose Agar (MPH581) after an initial incubation at 30-35°C for 24 hours. Typical pink colonies from MPH581 are subcultured for biochemical confirmation by oxidase and fermentation reactions (10).