PROCEDURE OF PRACTICAL SESSION

Task 1. To define the microbal number of the air by a sedimentation method (on Koch) and by an aspiration method (by the vehicle of Krotov).

Task 2. To define the microbal number of water of the opened reservoir.

Task 3. To define coli-index and coli-titre (plumbing) of drinking water by the fermentation method.

Task 4. To define coli-index (plumbing) of drinking water the method of membrane filters.

Task 5. To make off determination of microbial number of soil (for research used demonstration): to count up the amount of colonies, growing’s on cups with a meat-peptone agar, define the number of microbes in a 1 g of the investigated soil.

Task 6. To conduct microscopic research of kefir: to prepare painting, stain methylene blue, microscopic examination.

RECOMMENDATIONS FOR PRACTICAL WORK

Task 1.

Muddiness of air of the closed apartments is determined microbes on two indexes: 1) to the general amount of microbes, contained in a 1 m³ airs; 2) to high-quality composition of microflora of air, determined on the exposure of sanitary-indicatory bacteria (S. aureus and streptococci) and spore forming bacteria.

Finding out sanitary-indicator bacteria in mid air testifies to sanitary-epizootic and epidemiology prosperity, because they are selected from patients or bacilli carriers. Appearance of spore forming bacteria is an index of muddiness of airs the microorganisms of soil.

A sedimentation method (on Koch) is settling of microbes on the surface of dense nourishing media under the action of gravity. For research of air of apartments of Petri dish with media, open on 60 mines (for determination general semination air). Incubation air microbes in a thermostat at 37°C with during 24 hours and then at a room temperature (days). About the degree of muddiness of air judge on the amount of growing’s colonies, which count up, after determine the amount of microbes in a 1 m³ airs (microbial number) (look skim).

An aspiration method is more exact as compared to previous and used for research, both air of apartments and atmospheric air. For determination, general bacterial semination air of the closed apartments use two Petri dish with a meat-peptone agar and skip through a vehicle for 100 liter of air. After incubation during 48 h at a temperature 37°C with count up the amount of growing colonies on both Petri dish, calculate arithmetical mean and do a count on the amount of microbes in a 1 m³ airs by using a formula: X = a · 1000,

V , where a - is an amount of colonies; V - is the skipped volume of air (liter or dm3); 1000 – sought after volume of air (liter or dm3).

For you sowing of air was done (on the bottom of Petri dish an apartment is indicated). Do the count of microbial number. Enter a result in the minutes (write a conclusion about the cleanness of investigational air).

Task 2.

From the opened reservoirs the sample of water take away from a depth 10 — 15 sm from a surface and in the distance 10 — 15 sm from a bottom. Water is taken in sterile small bottles with a grinding cork by a capacity 0.5 liter. A tap water is poured after the preliminary kilning of faucet and flowing down of the first portions of water from him during 10 — 15 minutes. The interval of time from the moment of taking of test to the bacteriological examination must not exceed 2 h. (at a temperature 1 —5°C it is possible to keep to 6 h.).

A microbial number of water is an amount of microbes in 1 ml of in-use water — determine by inoculation waters on a meat-peptone agar.

The investigated water is conducted in 10, 100 and 1000 times. In a test tube with 9 ml of sterile water bring in 1 ml of the investigated water (dilution 1:10), after interfusion other pipette carry in an analogical test tube 1 ml of the divorced water (dilution 1 : 100) et cetera.

For 1 ml got diluting of water, since greater, carry in the marked sterile Petri dish and inundate 10 ml molten and frappe to 45°C a meat-peptone agar. Carefully circular motions are move the Petri dish on the surface of table, mixing content. Then the Petri dish with a hardening agar turns upside down and place on days in a thermostat. At research of tap water in each of two cups, inoculate 1 ml of non-dilution water. Growing’s in a layer and on-the-spot meat-peptone agar of colony of calculated, using magnifying glass, giving a fivefold increase, or vehicle for the semi-automatic count of colonies. At plenty of growing’s colonies (more 300) for the facilitation of count use a camera. For the receipt of microbial number, the amount of growing colonies is needed in Petri dish to increase waters on the proper breeding, to lay down the got results and divide into the amount of Petri dish.

Table 1

Date: 2016-01-14; view: 2146