COLI-INDEX, COLI-INDEX — the quantitative indices of fecal pollution of water, foodstuff, the soil and other objects of the environment based on a research of content of colibacillus in them.
Colibacillus (see) it is chosen as a sanitary and indicative microorganism since it in a significant amount is allocated with excrements to the environment where it is long remains and it can be easily isolated and identified. Presence of colibacillus at the studied substrates indicates a possibility of existence in them of others, including microorganisms of intestinal group, pathogenic for the person, which direct detection is complicated. High content of colibacillus in these or those substrates can demonstrate intensive fecal pollution and raises epidemiol. danger of these substrates. Therefore drinking water and various foodstuff are exposed constant sanitary bakteriol. to the control providing definition of a coli-index and coli-index.
Coli-index — the amount of colibacilli found in 1 l of liquid or 1 kg of solid matter (for foodstuff and the soil — in 1 g). The coli-index is defined by method of membrane filters or by direct crops of various amounts of the studied material on dense environments. The essence of a method of membrane filters consists in filtering of certain volumes of the studied liquid (or the solid matter divorced in water) via membrane filters No. 2 or No. 3 on which bacteria linger. Filters transfer to the cups with Endo's circle incubated at t°37 ° and then investigate grown by the surfaces of the filter dark red with metallic luster, and also pink and transparent colonies. From colonies of each type prepare smears and paint them across Gram. Colonies of different types check for oksidazny activity, edges shall be negative. Colourless and pink colonies in addition sow on the semi-fluid environment with glucose and the indicator, on a cut during a 24-hour incubation at t ° 37 ° acid and gas shall be formed. For definition of a coli-index count the colonies of colibacillus which grew on the filter and then carry out recalculation on 1 l, 1 kg or 1 g depending on the studied material. In the same way carry out studying of colonies and their calculation at direct seeding of material on Endo's circle.
Coli-index — the smallest amount of liquid or solid matter (expressed respectively in milliliters or grams), in Krom colibacilli are found. The coli-index is determined by the fermentative method consisting in crops of certain volumes of the studied substrate on Wednesdays accumulation which maintain at t ° 37 °. As environments of accumulation use the glyukozopeptonny or laktozopeptonny environment with the indicator and a float and other similar environments. Large volumes sow on the concentrated Wednesday, small volumes — in test tubes with normal-strength medium. Regardless of formation of acid and gas, do seedings on Endo's circle with the subsequent identification of the grown colonies of all dimmed test tubes.
Approximately take that smallest volume for a coli-index, at crops to-rogo on environments of accumulation colibacilli are revealed. The most probable value of a coli-index of water, milk, beer, etc. is defined by special calculation tables, comparing with them the received results. In general the fermentative method is less exact, than the accounting of the grown bacteria on dense environments and membrane filters.
A coli-index — size, the return to a coli-index which is a direct indicator of fecal pollution. Recalculation of a coli-index in a coli-index and back is possible. Marginal sizes of a coli-index (coli-index) of a normirovana all-union standard or republican technical specifications, and also special instructions of bodies of health care and other departments. E.g., in accordance with GOST 2874 — 73 coli-index on the drinking water arriving to consumers via cranes of a water supply system shall be no more than 3, and a coli-index not less than 300.
For obtaining more exact data on existence and extent of fecal pollution of objects it is considered it expedient to carry out along with definition of a coli-index (coli-index) the simultaneous quantitative account in the studied material and other sanitary and indicative microorganisms (e.g., a protea, enterococci, sporous anaerobe bacterias, intestinal bacteriophages); in some countries such complex definition is entered into practice at a sanitary bakteriol. research of water.
See also Microbic number .
Bibliography: Methods of a sanitary and microbiological research of objects of the environment, under the editorship of G. I. Sidorenko, M., 19 78; Sanitary microbiology, under the editorship of G. P. Guelder-rose and G. N. Chistovich, M., 1969.
N. S. Goryachkina.