MICROBIC NUMBER

From Big Medical Encyclopedia

MICROBIC NUMBER — a sanitary and microbiological indicator of the general level of microbic planting of objects of the environment — the soil, water, air, foodstuff, surrounding objects. The m of h is expressed by total number of the microorganisms capable to form visible colonies after seeding on dense mediums, in terms of 1 ml of the studied liquid, 1 g of dense substance, 1 m 3 air or 1 cm 2 surfaces. The m of h is not the term which is officially accepted for a dignity. - mikrobiol, normative documents and the managements where the indicator of the general microbic planting is designated more often as total number of microorganisms in 1 ml of water (in 1 g of a product). For definition of total quantity of microorganisms use also a method of the direct account under a microscope directly in the studied material or on membrane filters after a transmission of a certain water volume or washout and coloring of the filter. For the direct account of microorganisms in water also special automatic counters can be used (see. Avtoanalizatora ).

During the use of a method of the direct account of microorganisms receive the sizes exceeding those to-rye receive at calculation of the grown colonies. This results from the fact that at crops it is impossible to grow up at the same time all microorganisms which are present at the soil or water because of distinctions in requirements (sometimes opposite) to conditions of growth. Distinctions in the data obtained by two methods are maximum at a research of objects of the environment with flora, characteristic of it, and weak organic pollution and minimum — at a research of the objects contaminated by organic matters. In a dignity. - a gigabyte. to practice definition of the general microbic planting by method of crops (M.'s definition h) has major importance and it is widely used for control of a condition of water in the same source, efficiency of action of water treatment constructions, for control of foodstuff, etc. San. - a gigabyte. value of a method is defined by group of microorganisms, to-rye are considered by this equipment. During the seeding on a standard beef-extract agar and incubations during 24 — 72 hours at t ° 22 — 37 ° in aerobic conditions of colony form various group of microorganisms in the taxonomical relation, to-ruyu conditionally designate as saprophytic mesophilic aerobes and facultative anaerobes. They are combined by similar requirements to conditions of growth, the basic from to-rykh availability of organic matters is. Saprophytic aerobes and conditional anaerobe bacterias play a major role in processes of decomposition of organic matters in the nature, increasing quantitatively in process of pollution of the environment and decreasing at its clarification, in Krom they participate. The general level of microbic pollution along with definition a dignity. - indicative microorganisms serves as an indirect indicator of probability of hit to the environment of pathogenic microorganisms. Studying of dynamics of saprophytic microorganisms is included into the scheme of researches during the development of standards of the maximum allowable concentrations (MAC) of harmful substances in water and the soil. The method is irreplaceable for detection of receipt in a water supply system or drinking water of massive bacterial pollution.

For definition of total quantity of microorganisms in water directly or after a series of 10-fold cultivations do seedings in sterile Petri dishes within 0,1 — 1 ml of test of water. Then add to cups 12 — 15 ml melted and the beef-extract agar cooled to t ° 45 ° and, shaking, evenly mix an agar with water. Each cultivation is sowed on 1 — 2 cups. After hardening of an agar of a cup incubate depending on research objectives 24 hours at t ° 37 ° or 48 hours at t ° 20 — 22 °. For the account choose cups with number of colonies between 30 and 300. Total number of microorganisms in 1 ml is calculated taking into account the made cultivations and the sowed volume. For mains water standards established the general concentration of microorganisms no more than 100 in 1 ml of undiluted water.

For definition of the general microbic planting of the soil from a sample give 30 g and add 270 ml of sterile mains water; shake up 10 min. and part the uncontaminated soil to 10 - 3 , contaminated — to 10 - 5 — 10 - 6 (tenfold cultivations). Cultivations (not less than two) sow on Petri dishes and mix with the melted agar; incubate 48 hours at t ° 28 — 30 ° or 72 hours at t ° 22 °.

The research of air is conducted by means of Krotov's device (see. Samplers ) or seeding of liquid, through to-ruyu for catching of microorganisms passed a certain air volume.

For establishment of bacterial pollution of various surfaces use cotton plugs in test tubes from 2 ml of sterile mains water. Wipe with the humidified tampon the studied surface in 4 various places by means of a cliche of 25 cm 2 . The tampon is transferred to a test tube and add 8 ml of sterile mains water. After careful rinsing of a tampon water is sowed in a Petri dish with the melted agar. Apply also contact methods of a research, at to-rykh crops make contact of the studied surface with the surface of dense nutrient medium, to-ruyu then incubate before formation of colonies.

For a research of foodstuff use similar methods. Milk in the form of a series of 10-fold cultivations in isotonic solution of sodium chloride is sowed with the melted agar in Petri dishes and incubate at t ° 37 ° during the 48th hour. Firm foodstuff sows in an agar by the described technique after emulsification and cultivations in isotonic solution of sodium chloride. The stiffened agar is filled in from above with an additional thin coat of a hungry agar to prevent creeping growth like protea. For a number of foodstuff standards of the most admissible general concentration of microorganisms are established. At the characteristic of the products having the specific flora connected with the production technology (fermented milk products, fermented vegetables, kvass, etc.), h do not define M.



Bibliography: Wolpe I. M. and Kucherenko V. D. Practical guidance on sanitary microbiology, page 119, M., 1970; Hygiene of food, under the editorship of. K. S. Petrovsky, t. 1, page 490, M., 1971; Methods of a sanitary and microbiological research of objects of the environment, under the editorship of G. I. Sidorenko, page 5, M., 1978; Microbiology of contaminated waters, under the editorship of R. Mitchell, the lane with English, page 240, M., 1976; Minkh A. A. Reference book on sanitary and hygienic researches, M., 1973; Sanitary microbiology, under the editorship of G. P. Guelder-rose and G. N. Chistovich, page 13, M., 1969.


S. S. Belokrysenko.

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