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Abstract The increase in multi drug resistance (MDR) amongst food-borne pathogens such as Escherichia coli O157:H7, coupled with the upsurge of food-borne infections caused by these pathogens is a major public health concern. Lytic phages have been employed as an alternative to antibiotics for use against food-borne pathogens. However, for effective application, phages should be selectively toxic. Therefore, the objective of this study was to characterise lytic E. coli O157:H7 phages isolated from wastewater as possible biocontrol agents and access their genomes for the absence of genes that denotes virulence, resistance, toxins, and lysogeny using whole genome sequencing. E. coli O157:H7 bacteriophages showed clear plaques ranging in size from 1.0 mm to 2.0 mm. Spot test and Efficiency of plating (EOP) analysis demonstrated that isolated phages could infect various environmental E. coli strains. Four phages; vB_EcoM_EP32a, vB_EcoP_EP32b, vB_EcoM_EP57, and vB_EcoM_EP69 demonstrated broad lytic spectra against E. coli O157:H7 strains. Transmission Electron Microscopy (TEM) showed that all phages have tails and were classified as Caudoviricetes. Growth parameters showed an average latent period of 15 ± 3.8 min, with a maximum burst size of 392 PFU/cell. The phages were stable at three distinct temperatures (4 °C, 28 °C, and 37 °C) and at pH values of 3.5, 5.0, 7.0, 9.0, and 11.0. Based on their morphological distinctiveness, three phages were included in the Whole Genome Sequencing (WGS) analysis. WGS results revealed that E. coli O157:H7 phages (vB_EcoM_EP32a, vB_EcoP_EP32b, and vB_EcoM_EP57) were composed of linear double-stranded DNA (dsDNA) with genome sizes 163,906, 156,698, and 130,723 bp and GC contents of 37.61, 37, and 39% respectively. Phages vB_EcoM_EP32a and vB_EcoP_EP32b genomes were classified under the class Caudoviricetes, Straboviridae family, and the new genus “Phapecoctavirus”, while vB_EcoM_EP57 was classified under the class Caudoviricetes, Autographiviridae family. Genome analysis revealed no lysogenic (integrase), virulence, or antimicrobial resistance sequences in all three Escherichia phage genomes. The overall results provided evidence that lytic E. coli O157:H7 bacteriophages in this study, are relatively stable, can infect diverse E. coli strains, and does not contain genes responsible for virulence, resistance, toxins, and lysogeny. Thus, they can be considered as biocontrol candidates against MDR pathogenic E. coli O157:H7 strains in the food industry.

Shiga-toxin-producing Escherichia coli (STEC) is typically detected on food products mainly due to cross-contamination with faecal matter. The serotype O157:H7 has been of major public health concern due to the severity of illness caused, prevalence, and management. In the food chain, the main methods of controlling contamination by foodborne pathogens often involve the application of antimicrobial agents, which are now becoming less efficient. There is a growing need for the development of new approaches to combat these pathogens, especially those that harbour antimicrobial resistant and virulent determinants. Strategies to also limit their presence on food contact surfaces and food matrices are needed to prevent their transmission. Recent studies have revealed that bacteriophages are useful non-antibiotic options for biocontrol of E. coli O157:H7 in both animals and humans. Phage biocontrol can significantly reduce E. coli O157:H7, thereby improving food safety. However, before being certified as potential biocontrol agents, the safety of the phage candidates must be resolved to satisfy regulatory standards, particularly regarding phage resistance, antigenic properties, and toxigenic properties. In this review, we provide a general description of the main virulence elements of E. coli O157:H7 and present detailed reports that support the proposals that phages infecting E. coli O157:H7 are potential biocontrol agents. This paper also outlines the mechanism of E. coli O157:H7 resistance to phages and the safety concerns associated with the use of phages as a biocontrol.