The coliform index, e-coli

The coliform index, e-coli - quantitative indicators of fecal contamination of water, soil, food and other environmental objects. As an indicator of faecal contamination uses a permanent inhabitant of the human gut - E. coli, as it is easily grown in normal conditions on a simple nutrient media. The number of these bacteria allows to judge about the degree of faecal contamination of the test object.
The coliform index - the number of specimens of E. coli found in 1 l (for solids in 1 kg) investigated object; it is calculated by counting the E. coli colonies growing on nutrient dense environment while planting a certain number of investigated material, with the subsequent recalculation on 1 l (kg). The coliform index is a quantity proportional to the actual content of Escherichia coli in the study substrate.
E-coli is the least amount of investigated material in milliliters (for solids - in grams), in which there was one E. coli. To determine the number of the title separately sow liquid media tenfold decreasing the volume of the investigated material (for example, 100; 10; 1; 0,1; 0,01; 0,001 ml).
To transfer the number of the title in the coliform index should 1000 divided by the number expressing the e-coli; for translation coli-index in e-coli 1000 divided by the number expressing the coliform index.
For technical reasons, more often practiced defining the number of the title.
Defining the number of the title (coli-index) are important criteria in sanitary-hygienic assessment of water, food and drinks.