Characterization of polyvalent Escherichia phage Sa157lw for the biocontrol potential of Salmonella Typhimurium and Escherichia coli O157:H7 on contaminated mung bean seeds

Abstract

Seeds are one of the primary sources of contamination with foodborne pathogens, such as pathogenic Escherichia coli, and various Salmonella serovars, for produce, particularly sprouts. Due to the susceptibility of sprout growth to chemical-based antimicrobials and the rising issue of antimicrobial resistance, developing innovative antimicrobial interventions is an urgent need. Therefore, the objective of this study was to characterize Escherichia phage Sa157lw (or Sa157lw) for the biocontrol potential of Salmonella Typhimurium and E. coli O157:H7 on contaminated mung bean seeds. Phage Sa157lw was subjected to whole-genome sequencing and biological characterization, including morphology, one-step growth curve, and stress stability tests. Later, antimicrobial activity was determined in vitro and upon application on the mung bean seeds artificially contaminated with E. coli O157:H7 or Salmonella Typhimurium. Sa157lw possessed a contractile tail and belonged to the Kuttervirus genus under the Ackermannviridae family, sharing a close evolutionary relationship with E. coli phage ECML-4 and Kuttervirus ViI; however, tail spike genes (ORF_102 and ORF_104) were the primary region of difference. Comparative genomics showed that Sa157lw encoded a cluster of tail spike genes—including ORF_101, ORF_102, and ORF_104—sharing high amino acid similarity with the counterfeits of various Salmonella phages. Additionally, Sa157lw harbored a unique tail fiber (ORF_103), possibly related to the receptors binding of O157 strains. The genomic evidence accounted for the polyvalent effects of Sa157lw against E. coli O157:H7 and various Salmonella serovars (Typhimurium, Enteritidis, Agona, Saintpaul, and Heidelberg). Furthermore, the phage did not contain any virulence, antibiotic-resistant, or lysogenic genes. Sa157lw had a 30-min latent period on both E. coli O157:H7 and Salmonella Typhimurium, with an estimated burst size of 130 and 220 PFU/CFU, respectively, and was stable at a wide range of temperatures (4–60°C) and pH (pH4 to pH10). The phage application demonstrated a strong anti-E. coli O157:H7 and anti-Salmonella Typhimurium effects in 1.1 and 1.8 log reduction on the contaminated mung bean seeds after overnight storage at 22°C. These findings provide valuable insights into the polyvalent Sa157lw as a potential biocontrol agent of Salmonella Typhimurium and E. coli O157:H7 on sprout seeds.

Infectivity responses of Salmonella enterica to bacteriophages on maize seeds and maize sprouts

“…The findings were similar to a previous study where a single phage, Phage-A was applied on mustard seeds and a 1.37 log suppression of Salmonella growth was achieved ( Pao et al, 2004 ). In another study, phage application also demonstrated a strong anti- Salmonella Typhimurium effect in 1.8 log reduction on contaminated mung bean seeds after overnight storage at 22 °C ( Liao et al, 2022 ). Ye et al (2010) used a phage cocktail and achieved a higher Salmonella population reduction of ∼3.41 log CFU/g ( Ye et al, 2010b ).…”

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

“…Phage UDF157lw was purified through a cesium chloride (CsCl) gradient centrifugation to remove bacterial debris as previously described by Liao et al ( 2022b ). Phage DNA was extracted using a Norgen phage DNA extraction kit (Thorold, ON, Canada), followed by DNA library preparation before sequencing, as previously described by Zhang et al ( 2021 ).…”

“…The conservative (core) genes of UDF157lw were analyzed with the close-related reference phages using CoreGenes3.5 (Mahadevan et al, 2009 ). Phylogenetic analyses of the amino acid sequences were conducted on the major tail protein (ORF_26), tail fiber protein (ORF_35), holin (ORF_60), and lysozyme (ORF_61) using the methods previously described by Liao et al ( 2022b ). In brief, the amino acid sequences were aligned using ClustalW (version 1.2.3) from Geneious Prime.…”

“…CsCl-purified phage UDF157lw was subjected to negative staining and examined in a transmitted electron microscope (TEM, FEI Tecnai G2), as previously described by Liao et al ( 2022b ). In brief, 5 μl of the CsCl-treated phage was placed on a discharged 300 mesh carbon/formvar grid for 2-min absorption, followed by washing with distilled water and removing extra liquid.…”

Genomic and Proteomic Analysis of Six Vi01-like Phages Reveals Wide Host Range and Multiple Tail Spike Proteins

“…Since 2010, many more phages have been classified as Vi01-like and as of October 2023, we were able to identify a total of 150 Vi01-like phages that infect Enterobacteriaceae deposited in NCBI GenBank. Seventy of these Vi01-like phages appear in scientific articles in PubMed, primarily in genome announcements [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72...…”