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

Authors: Liao, Yen-Te; HO, KAN-JU - Forest Service (FS); Zhang, Yujie; Salvador, Alexandra; Wu, Vivian

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2023
Publication Date: 1/22/2024
Citation: Liao, Y., Ho, K., Zhang, Y., Salvador, A., Wu, V.C. 2024. A new Rogue-like Escherichia phage UDF157lw to control Escherichia coli O157:H7. Frontiers in Microbiology. 14. Article 1302032. https://doi.org/10.3389/fmicb.2023.1302032.
DOI: https://doi.org/10.3389/fmicb.2023.1302032

Interpretive Summary: Pathogenic Escherichia coli (E. coli), such as E. coli O157:H7, can cause severe illness after consuming contaminated food items and is closely associated with cross-contamination and poor sanitation. Biofilm contains a group of bacteria aggregated together on a surface and can render the bacterial cells extra protection against external stress, significantly diminishing the efficacies of antimicrobial interventions for sanitation. Due to the lytic nature of a bacteriophage (or phage), phage application poses a promising antimicrobial effect in mitigating different stages of bacteria, including biofilm. This study used genomic and biological approaches to study the antimicrobial potential of a lytic bacteriophage UDF157lw against E. coli O157:H7 biofilm. The results show that phage UDF157lw is a new phage with a long and non-contractile tail and belongs to the Rogunavirus genus. The phage does not contain harmful genes (virulence and lysogenic genes), which can compromise the safety upon application. The biological features indicate that phage UDF157lw has a narrow host range and only infects E. coli O157:H7. In addition, UDF157lw can produce an enzyme causing a halo ring around the lysis zone after infecting most E. coli O157:H7. In contrast to the phage without causing the halo ring, the enzymatic activity of UDF157lw shows antimicrobial effects against 24-h E. coli O157:H7 biofilm. The findings of this study provide insight into a new member of long-tailed-phages, UDF157lw, with potential anti-biofilm activity.

Technical Abstract: Shiga toxin-producing E. coli O157:H7 is the most notorious foodborne pathogen causing high mortality via consumption of contaminated food. The food safety risk from these 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, it is an urgent need to have alternative measurements for the control. Bacteriophages can kill the target bacterial cells through lytic infection, and some enzymes produced during the infection pose the capability to penetrate the biofilm for mitigation compared to traditional interventions. This study aimed to characterize a new phage, UDF157lw, via biological and genomic approaches and determine the phage's antimicrobial efficacy against E. coli O157:H7 biofilm. Phage characterization included biological—phage morphology, phage growth factor, and stability test (pH and temperature)—and genomic approaches (whole-genome sequencing). Later, antimicrobial activity tests were conducted, including the efficacy of plating (EOP) against susceptible bacterial strains and the application against E. coli O157:H7 (RM9995) biofilm. UDF157lw is a new Rogue-like phage isolated from bovine feces with a latent period of 15 min and a burst size of 110 pfu per infected cell against E. coli O157:H7 (ATCC 35150). The phage remained stable in the pH from pH4 to pH11 and temperature from 4°C to 65°C. No virulence genes, such as stx, and lysogenic genes, were found. The phage demonstrated high infection efficiencies against different E. coli O157:H7 and generic E. coli strains. Additionally, UDF157lw produced a large plaque size on various E. coli O157:H7 strains, showing enzymatic activity during phage infection. Furthermore, UDF157lw reduced the formation of the 24-h E. coli O157:H7 biofilm after 1-h phage treatment at 37°C. The findings of this study provide insight into a new member of the Rogue-like phages and show the antimicrobial potential of UDF157lw against E. coli O157:H7 biofilm.