M-EC Test Agar, 500 g

Examination of water, foods, ingredients and raw materials, for the presence of indicator groups such as coliforms is one of the most common tests in a microbiology laboratory, partly because of the relative ease and speed with which these tests can be accomplished. Where it is claimed that drinking water has been processed for safety, the finding of such organism demonstrates a failure of the process. It is a valuable bacterial indicator for determining the extent of faecal contamination of recreational surface waters or drinking water (1). M-EC Test Agar is recommended for the detection, differentiation and enumeration of Escherichia coli and coliforms in water using membrane filter technique (2). Proteose peptone and yeast extract provide necessary nutrients for the growth of coliforms. Lactose is the carbon source as well as fermentable carbohydrate in the medium. Sodium deoxycholate and sodium lauryl sulphate inhibit the growth of contaminating gram-positive microorganisms. Bromocresol purple and bromphenol red are the pH indicators. Filter the sample through a membrane filter. Place the membrane on M-EC Test Agar and incubate at 35 ± 0.5°C for 2 hours to rejuvenate injured or stressed bacteria and then incubate at 44.5 ± 0.2°C for 22 hours. Transfer filter to a filter pad saturated with urea substrate (Urea 2.0 g + phenol red 10 mg + distilled water 100 ml, adjust the pH between 3 and 4 use within one week). After 15 minutes, count yellow or yellow brown colonies using a fluorescent lamp and magnifying lens. E. coli produces yellow or yellow brown colonies.