Levintal environment (W. Levinthal) - special medium (agar, broth, blood agar) for the cultivation of bacteria that grow poorly on ordinary nutrient media.
Pre-cooked meat gruel - 100 g of meat passed through a meat grinder, pour 300 ml of sterile distilled water. The mixture is transferred to a bottle, 10 ml of a normal soda solution is added, mixed thoroughly and placed in a thermostat for 1-2 hours at 37—60 °. Add 0.5 g of pancreatin to 20-30 ml of water with 2 ml of normal soda solution and 10 ml of chloroform; the bottle is tied with parchment paper and left to stand for a day at 37 °, often shaking. To preliminarily determine the pH in a cone, mix 20 ml of thoroughly stirred-up meat gruel and 20 ml of buffer solution, boil for 1 minute. on fire and hot filtered through a paper filter; then cooled and determine the pH (should be 6.9-7.2).
To prepare the agar, a buffer solution of 8: 1000 dibasic sodium phosphate (Na 2 HPO 4 ) in distilled water, acidified with hydrochloric acid to pH = 5.6-6.6, is sterilized in a Koch apparatus. The solution is prepared with 3% agar and mixed in a saucepan with an equal volume of meat gruel. The mixture is heated over high heat and boiled for 1 min. Agar is decanted in a flask and re-boiled; hot filtered through a paper filter (the first portion twice) and alkalinized with a normal solution of soda to pH = 7.5-7.8; re-boil (preferably in small portions - 250 ml). Poured into sterile tubes and then sterilized in the Koch apparatus for 10-15 minutes. 3 days in a row.
Agar is used to cultivate meningococcus, gonococcus, Pfeifer sticks, etc.
For the preparation of broth, meat gruel and buffer solution are mixed in equal quantities, boiled, filtered, correct the reaction, boil again, poured into test tubes or flasks, sterilized in a Koch apparatus; peptone and salt are not added.
To prepare blood agar, 2% nutrient agar (pH = 7.3–7.5) is melted in a flask and cooled to 60 °, slowly, constantly shaking, 5–10% of defibrinated blood (horse, rabbit or human) is added sterilely, heated in the Koch apparatus at 100 °. Duration of heating 1 l - 5 min., 2 l - 8-10 min. Overheating of the agar is unacceptable: blood is precipitated and the medium becomes unsuitable. The medium can also be heated in a water bath: warm up for 2–3 minutes, remove, shake and reheat (only 2-3 times). The medium is precipitated for 2 hours. at 60 ° and the upper transparent layer is poured into cups. To make the medium transparent, it is filtered through a thin layer of non-greasy dressing cotton. Wednesday store no more than 3 weeks.
Apply environment for growing sticks of influenza.
See also Differential diagnostic media, Nutrient media.