Characterization and application of the lytic phage HHU8 for controlling Escherichia coli O157:H7 contamination across various food matrices

Abstract

Escherichia coli O157:H7 (E. coli O157:H7) is a commonly reported foodborne pathogen associated with severe illness from contaminated foods. Natural bacterial predators, such as bacteriophages (phages), are a promising alternative to traditional antimicrobial approaches. A lytic phage, HHU8, isolated from wastewater at a cattle farm was selected for further characterization. HHU8 showed high lytic activity against E. coli O157:H7 strains of various origins and maintained stability over a wide range of temperatures (4-55 °C) and pH (5-11). Biological characterization showed that HHU8 had an optimum multiplicity of infection (MOI) of 0.01, a latent period of 15 min, and a burst size of 283 ± 46 PFU/cell. Whole-genome sequencing revealed a genome size of 42,059 bp and the absence of virulence genes, antibiotic resistance determinants, or lysogeny-related factors. Functionally, HHU8 greatly inhibited E. coli O157:H7 biofilm formation in vitro and increased Galleria mellonella larvae survival after infection by 80% in vivo. In addition, HHU8 achieved maximum reductions in bacterial counts of 3.0, 2.4, 2.1, and 2.2 log in milk, lettuce, beef, and chicken, respectively, when applied to food matrices that had been artificially contaminated with E. coli O157:H7. All these results suggest that phage HHU8 is a safe and efficacious candidate for managing E. coli O157:H7 contamination in food systems.