Biological and genomic characterisation of phage Ec2-7 with antimicrobial activity against STEC strains Escherichia coli

Shigatoxin-producing Escherichia coli (STEC) is one of the leading causes of bacterial infections of foodborne origin, and the increasing antibiotic resistance of these strains requires the search for alternative control methods. The aim of the study was to characterize the new bacteriophage Ec2-7, using biological and molecular genetic approaches, to perform phylogenetic analysis and to evaluate its antimicrobial activity in vitro against STEC strain. Materials and Methods. Biological and genomic characterization of bacteriophage was carried out using common methods. DNA sequencing was performed on the Ion Proton platform, bioinformatic analysis was performed using RAST, VirulenceFinder, ResFinder, BLAST algorithm and NCBI nucleotide sequence databases. Phylogenetic analysis was performed using ViPTree and VIRIDIC platforms. Results. Bacteriophage Ec2-7 isolated from wastewater formed clear plaques 0.5—1 mm in diameter, had a high adsorption rate, short latency period (20 min), burst size 56±8 virions per cell and resistance to chloroform. It showed stability under aggressive conditions and exhibited lytic activity against STEC strains. According to whole genome sequencing, the Ec2-7 phage contained double stranded DNA of 146 kbp size with a G+C content of 38.9%. Phylogenetic analysis of the proteome (ViPTree) classified the phage as a member of the Pseudomonadota group, and comparative genomic analysis confirmed that it belonged to the genus Phapecoctavirus. Consequently, the absence of antibiotic resistance, virulence, and toxin genes within the genome was determined. In in vitro experiments, the Ec2-7 phage demonstrated antimicrobial activity, reducing STEC abundance by 99.7% within 6 hours after treatment. Conclusion. The combined characteristics of bacteriophage Ec2-7 indicated its potential for application in phage therapy and biocontrol of E. coli.