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Two Phages of the Genera Felixunavirus Subjected to 12 Hour Challenge on Salmonella Infantis Showed Distinct Genotypic and Phenotypic Changes

1
Escuela de Medicina Veterinaria, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago 8320000, Chile
2
Departamento de Ciencia de los Alimentos y Tecnología Química, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago 8380492, Chile
3
Department of Food Science, University of Tennessee, Knoxville, TN 37996, USA
4
Departamento de Medicina Preventiva Animal, Facultad de Ciencias Veterinarias, Universidad de Chile, Santiago 8330015, Chile
5
Escuela de Medicina Veterinaria, Facultad de Ciencias, Universidad Mayor, Santiago 8580745, Chile
6
Millennium Nucleus for Collaborative Research on Bacterial Resistance (MICROB-R), Santiago 7550000, Chile
*
Author to whom correspondence should be addressed.
Viruses 2019, 11(7), 586; https://doi.org/10.3390/v11070586
Received: 15 May 2019 / Revised: 23 June 2019 / Accepted: 25 June 2019 / Published: 27 June 2019
(This article belongs to the Special Issue Diversity and Evolution of Phage Genomes)
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Abstract

Salmonella Infantis is considered in recent years an emerging Salmonella serovar, as it has been associated with several outbreaks and multidrug resistance phenotypes. Phages appear as a possible alternative strategy to control Salmonella Infantis (SI). The aims of this work were to characterize two phages of the Felixounavirus genus, isolated using the same strain of SI, and to expose them to interact in challenge assays to identify genetic and phenotypic changes generated from these interactions. These two phages have a shared nucleotide identity of 97% and are differentiated by their host range: one phage has a wide host range (lysing 14 serovars), and the other has a narrow host range (lysing 6 serovars). During the 12 h challenge we compared: (1) optical density of SI, (2) proportion of SI survivors from phage-infected cultures, and (3) phage titer. Isolates obtained through the assays were evaluated by efficiency of plating (EOP) and by host-range characterization. Genomic modifications were characterized by evaluation of single nucleotide polymorphisms (SNPs). The optical density (600 nm) of phage-infected SI decreased, as compared to the uninfected control, by an average of 0.7 for SI infected with the wide-host-range (WHR) phage and by 0.3 for SI infected with the narrow-host-range (NHR) phage. WHR phage reached higher phage titer (7 × 1011 PFU/mL), and a lower proportion of SI survivor was obtained from the challenge assay. In SI that interacted with phages, we identified SNPs in two genes (rfaK and rfaB), which are both involved in lipopolysaccharide (LPS) polymerization. Therefore, mutations that could impact potential phage receptors on the host surface were selected by lytic phage exposure. This work demonstrates that the interaction of Salmonella phages (WHR and NHR) with SI for 12 h in vitro leads to emergence of new phenotypic and genotypic traits in both phage and host. This information is crucial for the rational design of phage-based control strategies. View Full-Text
Keywords: Felixounavirus; Salmonella virus FelixO1; Salmonella virus Mushroom; Salmonella Infantis; phage resistance mutants; host range; selective challenge assay Felixounavirus; Salmonella virus FelixO1; Salmonella virus Mushroom; Salmonella Infantis; phage resistance mutants; host range; selective challenge assay
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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    Doi: 10.5281/zenodo.3257780
    Description: Data_Supplementary Materials_viruses-516726
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MDPI and ACS Style

Rivera, D.; Hudson, L.K.; Denes, T.G.; Hamilton-West, C.; Pezoa, D.; Moreno-Switt, A.I. Two Phages of the Genera Felixunavirus Subjected to 12 Hour Challenge on Salmonella Infantis Showed Distinct Genotypic and Phenotypic Changes. Viruses 2019, 11, 586.

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