Antibiotically active material, which is not colicine, is isolated from a culture of strains of Escherichia Coli of high antibiotic activity against tubercle-bacilli by extraction with a solvent capable of dissolving lipoids, e.g. ether, petroleum ether, methylene chloride, ethyl acetate, methyl ethyl ketone and butanol.  The culture, the centrifuged bacteria or the culture centrifugate may be used.  The active material is obtained by removing the solvent. Extraction and recovery is preferably carried out at a temperature below 45 DEG  C.  The E. Coli are obtained by selecting antibiotically active strains cultivated in peptone - containing Hottinger culture medium and further cultivating such active strains in a culture medium containing protein, carbohydrate and nutrient salts substantially in the ratio of 1 : 3 : 0.9.  The culture medium may be whey of reduced protein content obtained by heating whey of pH 4.5 to 4.8 at 80 DEG  to 95 DEG  C., separating the precipitated protein, reheating the product at a pH 7.5 to 8.1 and 80 DEG  to 95 DEG  C. and separating the further precipitated protein.  In this material the nutrient salt is mainly sodium and potassium phosphates and the protein content 10 g./litre.  Peptones may be added up to 10 grams per litre of the prepared whey.  The Hottinger culture medium is obtained by digesting horsemeat with pancreatin, diluting with water and adding sodium chloride, K2HPO4 and peptone, the pH being adjusted to pH 7.2 to 7.5.  It is preferred to use three or more cultivation steps.  The temperature is 37 DEG  C., the pH is maintained at pH 7.2\sB0.2 by the addition of alkali, e.g. ammonia, and the culture medium is stirred and aerated. Cultivation is continued until the bacteria have multiplied in the whey medium by a factor of 1000 to 10,000.ALSO:Strains of Escherichia coli of high antibiotic activity against tubercle-bacilli are obtained by selecting antibiotically active strains from E. coli cultivated in peptone-containing Hottinger culture medium, further cultivating such active strains in a culture medium containing protein, carbohydrate and nutrient salts substantially in the ratio of 1 : 3 : 0.9 and thereafter separating the antibiotically active strains of E. coli from such medium.  The culture medium may be whey of reduced protein content obtained by heating whey of pH 4.5 to 4.8 at 80 to 95 DEG C., separating the precipitated protein, reheating the product at a pH 7.5 to 8.1 and 80 to 95 DEG  C. and separating further precipitated protein.  In this material the nutrient salt is mainly sodium and potassium phosphates and the protein content 10 g/litre. Peptones may be added up to 10 grms per litre of the prepared whey. The Hottinger culture medium is obtained by digesting horsemeat with pancreatin, filtering, diluting with water and adding sodium chloride, K2HPO4 and peptone, the pH being adjusted to 7.2 to 7.5. Preferably three or more cultivation steps are used; the temperature is 37 DEG  C., the pH is maintained at 7.2\sB0.2 by the addition of alkali preferably ammonia, and the culture medium is stirred and aerated. Cultivation in the whey medium is continued until the bacteria have multiplied by a factor of 1,000 to 10,000.  A suspension of the bacteria obtained by centrifuging the culture medium may be suspended in water or saline and applied as a rectal douche. Alternatively, antibiotically-active extracts may be prepared (see Group IV (b)).