Determination of lytic activity of coli-bacteriophage

The standard system has been elaborated for the control of lytic activity of the commercial series - active coli- bacteriophage and respective stable E. coli strains' collection. Special investigations were carried out with an aim to obtain polyvalent bacteriophage, which should comply with the requirements for the standard preparations. While passing of the active phage on the highly reproducible standard strain the coli-bacteriophage phage-lysate was obtained. With an aim to preserve its basic properties the phage-lysate has been lyophilized. The 20% Difco-peptone was used as the stabilizer. The lyophilized bacteriophage completely satisfies the parameter standards for biological preparations: it has high lytic activity, wide range of action, and thermal resistance. These properties are reliably preserved for the period of three years. It was shown experimentally that the lyophilized cultures could be used for evaluation of the lytic activity in bacteriophages. The identical phage-sensitivity was revealed in both lyophilized- and agar-cultures.