Salmonella Typhimurium-specific bacteriophage ΦSH19 and the origins of species specificity in the Vi01-like phage family

Steven Pt Hooton,Andrew R Timms,Ray Wilson,Joanna Rowsell,Ian F Connerton

doi:10.1186/1743-422x-8-498

Steven Pt Hooton, Andrew R Timms + Show 3 more

Open Access

https://doi.org/10.1186/1743-422x-8-498

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Abstract

BackgroundWhole genome sequencing of bacteriophages suitable for biocontrol of pathogens in food products is a pre-requisite to any phage-based intervention procedure. Trials involving the biosanitization of Salmonella Typhimurium in the pig production environment identified one such candidate, ΦSH19.ResultsThis phage was sequenced and analysis of its 157,785 bp circular dsDNA genome revealed a number of interesting features. ΦSH19 constitutes another member of the recently-proposed Myoviridae Vi01-like family of phages, containing S. Typhi-specific Vi01 and Shigella-specific SboM-AG3. At the nucleotide level ΦSH19 is highly similar to phage Vi01 (80-98% pairwise identity over the length of the genome), with the major differences lying in the region associated with host-range determination. Analyses of the proteins encoded within this region by ΦSH19 revealed a cluster of three putative tail spikes. Of the three tail spikes, two have protein domains associated with the pectate lyase family of proteins (Tsp2) and P22 tail spike family (Tsp3) with the prospect that these enable Salmonella O antigen degradation. Tail spike proteins of Vi01 and SboM-AG3 are predicted to contain conserved right-handed parallel β-helical structures but the internal protein domains are varied allowing different host specificities.ConclusionsThe addition or exchange of tail spike protein modules is a major contributor to host range determination in the Vi01-like phage family.

Highlights

Whole genome sequencing of bacteriophages suitable for biocontrol of pathogens in food products is a pre-requisite to any phage-based intervention procedure
The use of virulent bacteriophages as biological control agents against bacterial pathogens is an expanding field of research aimed at producing sustainable solutions for the control of these pathogens, and to circumvent problems such as those associated with the development of multidrug-resistant bacteria [1]
The antimicrobial activities of phages committed to the cellular lysis of a range of bacterial pathogens have been reported, which include food pathogens such as Campylobacter jejuni [2,3,4,5], Escherichia coli [6,7,8], and various Salmonella enterica serovars [4,9,10]

Summary

Introduction

Whole genome sequencing of bacteriophages suitable for biocontrol of pathogens in food products is a pre-requisite to any phage-based intervention procedure. The antimicrobial activities of phages committed to the cellular lysis of a range of bacterial pathogens have been reported, which include food pathogens such as Campylobacter jejuni [2,3,4,5], Escherichia coli [6,7,8], and various Salmonella enterica serovars [4,9,10]. Phage P100 (the active component of Listex P100) was initially characterized at the genetic level and in oral toxicity studies by Carlton et al [12]. These studies showed that P100 had no undesirable genes within its genome, and caused no ill effects when administered to rats. Many studies reporting the efficacy of Listex P100 against L. monocytogenes in various food production settings are available in the literature [13,14,15]

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