Plasmid profile, colicinogeny and phage sensitivity as indicators of the dynamics of Escherichia coli populations in the human gut.

A possibility to use such bacterial phenotypes as plasmid profiles, colicinogeny and phage sensitivity as dynamics indicators of enterobacterial population in the human intestine was considered in the present work. All these three phenotypes, considered together with the type of enterobacterial association and age of the patients may reflect the dynamic state of the individual E. coli population that is currently prevailing in the intestinal microflora. The data on plasmid profile structure, colicinogeny and phage sensitivity indicate to considerable quantitative and qualitative diversity of E. coli genetic elements and the intensive interaction between bacteria in the human gut. This diversity is reflected on the formation of the dynamic population of intestinal bacteria, which obviously depends on the host age. The evaluation of the three above mentioned phenotypes confirmed that the E. coli isolates are closely coordinating with other members of the intestinal microbial association. It is noted that the plasmid frequency increases, the colicin range expands and phage sensitivity decreases in E. coli cells simultaneously with the increase of the number of enterobacterial species in the gut. The dynamics of changes in the biological features was observed among E. coli strains from different age groups of patients. The most significant was high frequency of colicinogenic strains in adult patients and di-associated E. coli containing one large plasmid in the youngest patients with dysbiosis.

[Plasmid spectra and phagotypes of Escherichia coli strains isolated from patients with large intestine tumours]. / Plazmidnye spektry i fagotipy shtammov Escherichia coli, vydelennykh ot bol'nykh s opukholiami tolstogo kishechnika.

The work deals with connection between plasmid spectra and phagotypes of Escherichia coli strains isolated from patients with tumours in large intestine. It has been established that 70 % of this bacterium isolates from the normal tissue, intestine lumen and tumours are characterized by multiple content of plasmids. Sometimes large endogenic plasmids are accompanied by the closed ring DNA with discrete sizes: 3.2; 3.8 and 4.0 kb. Other extrachromosomal factors have the size of 63-119 kb and are divided into 5 discrete classes. Plasmid DNA which size is 69 and 119 kb occur rarely and are characteristic of only E. coli isolated from the tumour tissue. Cells of three isolates found in the tissues and intestine lumen contain a plasmid complex which consists of three different extrachromosomal DNA of 63, 82 and 102 kb. The complex availability correlates as a rule with multiple strain resistance to ampicillin, canamycin, and tetracycline. Variability of plasmids of clinical E. coli isolates is completed regularly by various phagotypes established by means of virulent bacteriophages T2, T4, T7, FE44, TuIb, Ox2 and MS2. In most cases one could trace interrelation between the plasmid spectrum and phagotype; the same phagotype includes the strains with the same set of plasmids. The work results create preconditions for the detailed study of the role of microbe factor in development and inhibition of tumours.