M-FC Medium (Economy pack) (without Membrane Filter)

Principle And Interpretation

Field of Application: Water (Standard TNV 75, 7835, 1999), food. DriFilter Membrane Nutrient Pad Medium is ready to use sterile culture media in the form of a 50 mm biological inert absorbent pads impregnated with M-FC medium, then dried and sterilized in 55 mm petri plate. They eliminate the need of laborious media preparation and autoclaving procedures. The nutrient pads are to be just rewetted with sterile distilled water and are ready to use. Use of nutrient pads allows larger sample volumes to be tested at a time. Interpretation of results is directly by counting the CFUs and also quantifies the microbial load present in the sample. M-FC Medium, designed by Geldreich et al (2) is used for the detection and enumeration of faecal coliforms using the membrane filter technique. This medium is based on the property of faecal coliforms to grow at 44-45°C (1). M-FC Medium is recommended by APHA (3) and by various other standards for detection of faecal coliforms (4-6). APHA recommends the membrane filtration procedure and delayed incubation for faecal coliforms. Proteose peptone, tryptose and yeast extract provide necessary nutrients for the growth of faecal coliforms. Lactose is the carbon source as well as fermentable carbohydrate in the medium. Bile salts inhibit the growth of contaminating gram-positive microorganisms. Aniline blue is a triphenyl methane dye which suppresses the growth of many gram positive microorganisms. Aniline blue along with rosolic acid forms the indicator system of the medium. Membrane filters, through which water sample is passed, are aseptically placed onto M-FC Medium plates. If total coliforms are to be estimated, incubation is carried out at 35-37°C whereas if faecal coliform count is to be stimated, incubation is done at 44-45°C. Coliforms will form blue colonies whereas non-coliforms will form gray coloured colonies on M-FC Medium.