A new Rogue-like phage UDF157lw to control O157:H7.

Introduction: Shiga toxin-producing (STEC) O157:H7 is one of the notorious foodborne pathogens causing high mortality through the consumption of contaminated food items. The food safety risk from STEC pathogens could escalate when a group of bacterial cells aggregates to form a biofilm. Bacterial biofilm can diminish the effects of various antimicrobial interventions and enhance the pathogenicity of the pathogens. Therefore, there is an urgent need to have effective control measurements. Bacteriophages can kill the target bacterial cells through lytic infection, and some enzymes produced during the infection have the capability to penetrate the biofilm for mitigation compared to traditional interventions. This study aimed to characterize a new phage vB_EcoS-UDF157lw (or UDF157lw) and determine its antimicrobial efficacy against O157:H7.

Methods: Phage characterization included biological approaches, including phage morphology, one-step growth curve, stability tests (pH and temperature), and genomic approaches (whole-genome sequencing). Later, antimicrobial activity tests, including productive infection against susceptible bacterial strains, antimicrobial activity, and anti-biofilm, were conducted.

Results: UDF157lw is a new member of the phages belonging to the genus, comprising a long and non-contractile tail, isolated from bovine feces and shares close genomic evolutionary similarities with phages vB_EcoS-BECP10 and bV_EcoS_AKS96. When used against O157:H7 (ATCC35150), phage UDF157lw exhibited a latent period of 14 min and a burst size of 110 PFU per infected cell. The phage remained viable in a wide range of pH values (pH 4-11) and temperatures (4-60°C). No virulence genes, such as , lysogenic genes, and antibiotic resistance genes, were found. Phage UDF157lw demonstrated high infection efficiencies against different O157:H7 and generic strains. In addition, UDF157lw encoded a unique major tail protein (ORF_26) with prominent depolymerase enzyme activity against various O157:H7 strains, causing large plaque sizes. In contrast to the phage without encoding depolymerase gene, UDF157lw was able to reduce the 24-h and 48-h O157:H7 biofilm after 1-h phage treatment.

Discussion: The findings of this study provide insights into a new member of the phages and demonstrate its antimicrobial potential against O157:H7 .