[Using the laboratory strains of Escherichia coli for studying colicinogenicity]

The indicator system which includes laboratory strains of Escherichia coli K12, K12-C600, BE, and C-Ia is offered for studying colicinogenicity. It has helped to establish that 32 of 100 patients with dysbacterioses of colon carry a colicin-producing strain of E. coli. A tendency is discovered to the increase of occurrence of colicinogenic strains of escherichias with patients' age. Only 24% of E. coli strains form active colicins in a group of one-year old children. Frequency of colicinogenic strains occurrence increases to 33 and 42 %, respectively, in teenagers and adult patients. A strict decrease of total activity of colicins is the main peculiarity of polymicrobe associations in which the prevailing strain of E. coli is accompanied by 3-5 strains of other enterobacteria. As to their sensitivity of colicins the indicator strains are arranged in the following order: K12-C600 (84%), KR (69%), BE (63%) and C-Ia (47%). In spite of that, the low-sensitive strains can be effective for identification of very specific colicins. Since the laboratory strains of E. coli K12, BE and C-Ia are the hosts for specific bacteriophages of E. coli, the indicator system on their basis may be useful for studying the interrelation between colicins and coliphages, as well as plasmids and restriction-modification systems. The paper is presented in Russian.