Characterization of a lytic bacteriophage as an antimicrobial agent for biocontrol of Shiga toxin-producing Escherichia coli O145 strains

Authors: Liao, Yen-Te; Salvador, Alexandra; Harden, Leslie - Les; LIU, FANG - Ocean University Of China; Lavenburg, Valerie; Li, Robert; Wu, Vivian

Submitted to: Antibiotics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2019
Publication Date: 6/5/2019
Citation: Liao, Y., Salvador, A., Harden, L.A., Liu, F., Lavenburg, V.M., Li, R.W., Wu, V.C. 2019. Characterization of a lytic bacteriophage as an antimicrobial agent for biocontrol of Shiga toxin-producing Escherichia coli O145 strains. Antibiotics. 8(2):74. https://doi.org/10.3390/antibiotics8020074.
DOI: https://doi.org/10.3390/antibiotics8020074

Interpretive Summary: Lytic bacteriophages (or phages) have been used as alternative intervention measures to control bacterial pathogens, such as Shiga toxin-producing E. coli (STEC) strains, which are capable of causing severe illness, including bloody diarrhea and hemorrhagic uremic syndrome, and have been associated with produce outbreaks around the world. Although there are increasing numbers of lytic bacteriophages isolated from the environment, those specific against STEC O145 with further characterization are scarce. Current study focused on characterization of a lytic bacteriophage—vB_EcoS-Ro145clw—using whole-genome sequencing and proteomic and analyzed the potential as a biocontrol agent for Shiga toxin-producing E. coli O145 strains. The results of this study show that the phage vB_EcoS-Ro145clw has a narrow host range, specific against STEC serogroup of O145, with the morphology belonging to Siphoviridae family. The genomic results indicate that the phage genome has 68 predicted genes in which no virulence genes, such as stx genes and antimicrobial resistance genes were found. Furthermore, the phage vB_EcoS-Ro145clw shows strong lytic effects against various STEC O145 strains, and the biological features of the phage indicate a short replication time (20min) and a huge burst size (722 phage particles per infected bacterial cell). The findings of this study demonstrate that phage vB_EcoS-Ro145clw equips with prominent antimicrobial features to be used as a novel biocontrol agent for STEC O145 strains.

Technical Abstract: Shiga toxin-producing E. coli (STEC) O145 is one of the most prevalent non-O157 STEC strains, besides E. coli O157:H7, commonly associated with produce outbreaks in the United States and other countries. Due to the abuse usage of antibiotics, there are growing numbers of interests to explore alternative intervention methods to control bacterial pathogens without contributing to the development of antibiotics resistance. In light of lytic feature, bacteriophages are able to multiply rapidly in the presence of the bacterial host and have been recently considered as alternative antimicrobial agents for bacterial pathogens. Although there are more and more lytic bacteriophages isolated from the environment, those specific against STEC O145 with further characterization are scarce. Therefore, the objective of this study was to isolate and characterize a bacteriophage from non-fecal compost as a novel biocontrol agent for STEC O145 strains. Escherichia phage vB_EcoS-Ro145clw (or Ro145clw) was isolated from non-fecal compost and subjected to whole genome sequencing (Illumina Miseq) and proteomic analyses. Biological characteristics, such as morphology, temperature stability, latent period, adsorption rate and burst size, were exanimated. The antimicrobial activities of the phage were determined by using host range test, efficiency of plating and bacterial challenge assay. The results show that Ro145clw, belonging to Siphoviridae family but unclassified at genus level, contains 42031bp of a double-stranded genome with a G+C content of 50.6%. There are 68 open reading frames (ORFs) predicted in which none of those contain stx genes or antibiotic resistance genes. Proteomic analysis indicates that the most abundant proteins in the phage are tape measure protein, major capsid protein and tail protein. The phage Ro145clw is specific to the serogroup of O145 and able to render strong lytic effects against all the selected environmental and one outbreak strains of STEC O145. Additionally, with a short infection time (latent period of 20 min), high stability at 73'C for 60 min and huge burst size (722 pfu per infected cell), this phage vB_EcoS-Ro145clw is shown to be a good biocontrol agent for STEC O145 strains.