EE Broth, Mossel, Granulated

Principle And Interpretation

The family Enterobacteriaceae consists of Salmonella, Shigella and other enteric pathogens. These organisms find entry into the foodsystem through faecally contaminated water. Majority of these organisms may be eliminated under the stringent food processing parameters. But some of these organisms may become sublethally injured during the changes in pH, exposure to steam or heat and other unfavourable conditions (1). Therefore the important aspect of food monitoring depends upon the identification and enumeration of these injured cells, after resuscitation. EE Broth, Mossel, formulated by Mossel et al (2) is recommended as an enrichment medium for Enterobacteriaceae in the biological examination of foods (2) and animal feed stuffs (3).

Peptic digest of animal tissue and dextrose provide the essential nutrients required for the growth of most of the members of Enterobacteriaceae. Brilliant green and ox bile, purified inhibit growth of gram-positive bacteria. 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 dextrose in these media. Phosphates form the buffering system of the medium. The cells damaged while drying or low pH are resuscitated in well-aerated Tryptone Soya Broth (GM011/M011) for 2 hours at 25°C prior to enrichment in EE Broth. The resuscitation procedure is recommended for dried foods (5), animal feeds (6) and semi-preserved foods (7). EE Broth is an enrichment broth and should be used in conjunction with Violet Red Bile Glucose Agar (GM581/M581). Subcultures must be made onto lactose differential media such as MacConkey Agar (GM081/M081), Deoxycholate Citrate Agar (GM065/M065) or Brilliant Green Agar (GM016A/M016) for the detection of lactose negative or delayed lactose fermenters. This is used to inoculate MPN tubes prepared using EE Broth. Inoculate a loopful from these tubes onto Violet Red Bile Glucose Agar (GM581/ M581) after an initial incubation at 35-37°C for 24 hours. Typical pink colonies from GM581/M581 are subcultured for biochemical confirmation by oxidase and fermentation reactions (4). Decimal dilutions of the food homogenate are used if the expected counts are high or else initial suspension is used.EE Broth, Mossel (GM287/M287).