Location: Produce Safety and Microbiology ResearchTitle: Characterization of a Lytic Bacteriophage as an Antimicrobial Agent for Biocontrol of Shiga Toxin-Producing Escherichia coli O145 Strains
|Harden, Leslie - Les
|LIU, FANG - Ocean University Of China
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2019
Publication Date: N/A
Technical Abstract: Shiga toxin-producing E. coli (STEC) O145 is one of the most prevalent non-O157 serogroups associated with foodborne outbreaks besides E. coli O157:H7. Due to the biocontrol potential, lytic phages have been considered as promising and alternative antibacterial agents to combat bacterial pathogens and to prevent the emergence of antimicrobial resistance strains. However, few phages specific to STEC non-O157, as compared to E. coli O157:H7, have been characterized and simultaneously evaluated its in vitro antimicrobial effects. Thus, the objective of this study was to characterize a bacteriophage isolated from non-fecal compost and examine its potential as a novel biocontrol agent to control STEC O145 strains. Escherichia phage vB_EcoS-Ro145clw (or Ro145clw) was isolated from the enrichment of non-fecal compost with a 14-STEC strain cocktail in CaCl2-added tryptic soy broth at 37'C incubation for 24 h. Phage was purified and concentrated prior to biological (TEM, one-step growth curve, pH and temperature susceptibility test) and genomic characterization using whole-genome sequencing (Illumina MiSeq). De novo assembly was conducted using SPAdes algorithm, and the genome annotation was subjected to Prokka workflow. Subsequently, in vitro antimicrobial activity against an outbreak strain—E. coli O145:H28—was evaluated. Lysogeny test of the phage was also determined after infection of the strain. Ro145clw, belonging to family Siphoviridae, has a double stranded DNA in 42031-bp length and encodes 68 genes in which 19 were annotated with functional proteins, including one potential lysogenic factor: transcriptional repressor DicA. No genes coding for Shiga toxin or antibiotic resistance factors were found. The phage, specific against the serogroup of STEC O145, has latent period of 20 min and burst size of 192 phage particles per infected cell and is stable at 73'C for 1 h and in adverse pH (from pH5 to pH 10) for 24h. Though presence of potential lysogenic factor, the lysogeny test results showed that Ro145clw did not form lysogen after infection of E. coli O145:H28. Ro145clw was able to reduce E. coli O145:H28 in LB broth by approximately 5 log10 CFU/ml at 37'C in 4 h. The findings of this study indicate the phage Ro145clw is a promising antimicrobial agent that can be used in the condition with adverse pH and temperature to control pathogenic E. coli O145.