Isolation of broad-host-range bacteriophages against food- and patient-derived Shiga toxin-producing Escherichia coli

This study aimed to isolate bacteriophages specific to Shiga toxin-producing Escherichia coli (E. coli) strains, particularly EHEC O157:H7, in order to develop a collection of phages against different E. coli pathotypes isolated from northeast of Iran. Eighteen samples were screened without any preliminary enrichment and also with small scale enrichment using E. coli 12900, which did not result in the phage recovery. Seven samples were prepared with an extensive enrichment. Of them, 5 samples produced plaques. Eventually, seven phages out of thirteen isolated phages were selected for phage host range investigation. Results of the spotting host range assay demonstrated that 22 pathogenic E. coli strains and isolates (54%) were susceptible to at least one of the phages. Phage Ecol-MHD1 was polyvalent against E. coli and Salmonella isolates. The other phages were specific to E. coli pathotypes. In conclusion, the phages isolated in this study can be suggested as preventive or therapeutic candidates against foodborne E. coli infections in humans.