Evaluation of C-EC-agar, a modified mFC-agar for the simultaneous enumeration of faecal coliforms and Escherichia coli in water samples

A new medium, C-EC-agar (Biolife, Milan, Italy), was evaluated for the simultaneous enumeration by membrane filtration of faecal coliforms and Escherichia coli in water. The medium is a modification of m-faecal coliform agar, from which the aniline blue and lactose have been omitted and 4-methylumbelliferyl-β-D-glucuronide, 5-bromo-4-chloro-3-indolyl-β- d -galactopyranoside and isopropyl-β- d -thiogalactoside added. At 44°C E. coli gives blue-green colonies that fluoresce under u.v.-light (366 nm) and give a reddish-violet colour when Kovac's reagent is placed on the membrane. Under similar conditions, faecal coliform colonies do not fluoresce. To increase recovery on the medium, repair of sub-lethally injured cells by a 4-h incubation at 37°C on tryptic soy agar is recommended.