From Big Medical Encyclopedia

CHRISTENSEN OF THE ENVIRONMENT (W. Christensen) — the complex agarizovanny nutrient mediums intended for differentiation of enterobakteriya.

Citrate and sulphidic agar of Christensen

Structure: sodium citrate — S g, glucose — 0,2 g, a yeastrel — 0,5 g, cysteine muriatic — 0,1 g, monosubstituted potassium phosphate — 1 g, sodium chloride — 5 g, sodium thiosulphate — 0,08 g, ferric ammonium citrate — 0,4 g, phenol red — 0,012 g, an agar — 15 g, a distilled water — 1000 ml. Final pH of the environment — 6,7.

Previously all salts dissolve in small water volumes, then merge together and add an agar. After swelling of an agar mix is boiled before dissolution of an agar, filtered and add 0,4% solution of dye (3 ml on 1 l of the environment). Wednesday is spilled in test tubes and sterilized within 15 min. at 1 atm. After sterilization of a test tube leave before hardening of the environment in inclined situation so that the column and a beveled surface in the ratio 1:2 was formed. Ferric ammonium citrate and sodium thiosulphate can be in case of need excluded.

Crops of culture is made on all beveled surface of the environment.

Cultivation is conducted at t ° 37 ° within 7 days. With a growth of a number of pathogenic bacteriums (causative agents of a typhoid, paratyphus, dysentery, food toxicoinfections, and also Proteus) the surface of the environment is painted in red color, with a growth of colibacillus — in yellow color.

Ureal circle of Christensen

Structure: peptone — 1 g, sodium chloride — 5 g, glucose — 1 g, monosubstituted potassium phosphate — 2 g, phenol red — 0,012 g, urea — 20 g, a distilled water — 100 ml. The concentrate of urea prepared by way of consecutive dissolution of the specified ingredients is carried to pH=6,8 and will be sterilized by filtering via Zeytts's filter.

15 g of an agar dissolve in 900 ml of a distilled water, autoclave 15 min. at 1 atm and cool on the water bath to t ° 55 °. Then to the cooled agar flow 100 ml of a sterile concentrate of urea. The Wednesday prepared thus is spilled in test tubes and cooled (before hardening) in inclined situation that the column and a beveled surface in the ratio 1:2 were formed.

Crops of culture is made a lawn on a slanted part of the environment. Cultivation conduct at t ° 37 °C the accounting of results in 2, 4 and 18 hour. Of not changed color it is necessary to leave test tubes with Wednesday on 4 days with daily viewing for the purpose of identification of the slowed-down reaction, to-ruyu representatives of certain groups of the bacteria different from Proteus give.

The bacteria splitting urea alkalinize Wednesday therefore it is painted in red color.

See also Mediums .

Bibliography: The reference book on microbiological and virologic methods of a research, under the editorship of M. O. Birger, M., 1973; Christensen W. Urea decomposition as means of differentiating proteus and paracolon cultures from each other and from Salmonella and Shigella types, J. Bact., y. 52, p. 461, 1946; Manual of clinical microbiology, ed. by E. H. Lan-nette a. o., p. 881, Washington, 1974.

Yu. K. Fomichev.