AGAR EMB X 500 GRS

Levine EMB Agar was formulated by Levine (1, 2) is used for the differentiation of Escherichia coli and Enterobacter aerogenes and also for the rapid identification of Candida albicans. This medium is recommended for the detection, enumeration and differentiation of members of family Enterobacter iaceal by American Public Health Association (3-5). Weld (6, 7) proposed the use of Levine EMB Agar, with added Chlortetracycline hydrochloride, for the rapid identification of Candida albicans from clinical specimens. A positive identification of Candida albi cans can be made after 24 – 48 hours incubation at 35 – 37°C in 10% carbon dioxide atmosphere, from specimens such as faeces, oral and vaginal secretions and nail or skin scraping etc. However, the typical appearance of colony on the media is variable.
Eosin Y and methylene blue make the medium slightly selective and inhibit the growth of certain gram-positive bacteria. These dyes serve as differential indicators in response to the fermentation of carbohydrates. This helps to differentiate between lactose-ferment ere and non- fermenters in EMB Agar, Levine. The ratio of eosin-methylene blue is adjusted to approximately 6:1. Lactose-fermenting Coliforms produce purplish black colonies due to uptake of methylene blue-eosin dye complex,
when the pH drops. Non-fermenters probably raise the pH of surrounding medium by oxidative de-amination of protein, which solubilizes the methylene blue-eosin complex resulting in formation of colourless colonies (8). Some strains of Salmonella and Shigella species do not grow in the presence of eosin and methylene blue.
Peptic digest of animal tissue serves as source of carbon, nitrogen, and other essential growth nutrients. Lactose serves as the source of energy by being the fermentable carbohydrate. Eosin-Y and methylene blue serve as differential indicators. Phosphate buffers the medium. The test sample can be directly streaked on the medium plates. Inoculated plates should be incubated, protected from light. H owever standard procedures should be followed to obtain isolated colonies. A non-selective medium should be inoculated in conjunction with EMB Agar. Confirmatory tests should be further carried out for identification of isolated colonies.