title: Physiological and Molecular Characterization of Salmonella Bacteriophages Previously Used in Phage Therapy.
abstract: The use of bacteriophages as biocontrol agents to control Salmonella in food production has gained popularity over the last two decades. Previously, our laboratory demonstrated that bacteriophages can be direct fed to limit Salmonella colonization and transmission in pigs. Here, we characterized the bacteriophages in our treatment cocktail in terms of lytic spectrum, growth kinetics, survivability under various conditions, and genomic sequencing. PCR-based fingerprinting indicated that 9 of the 10 phages, while related, were distinct isolates. Single-step growth kinetics analysis determined that the eclipse periods, latent periods, and burst sizes averaged 21.5 min, 31.5 min, and 43.3 particles, respectively. The viability of the phages was measured after exposure to various pH ranges, temperatures, digestive enzymes, UV light, and chlorinated water. Temperatures greater than 87.5°C, pH of <2.0, UV light (302 and 365 nm), and chlorinated water (500 ppm) inactivated the tested phages. Only select bacteriophages, however, were affected by incubation at temperatures of ≤75.0°C or pH of 4.0 to 10.0. Genomic sequencing of the phage with the broadest spectrum in the collection (effectively lysed all four Salmonella serovars tested), vB_SalM_SJ2, revealed it to belong to the Viunalikevirus genus of the Myoviridae family. Of the 197 predicted open reading frames, no toxin-associated, lysogenic, Salmonella virulence, or antimicrobial resistance genes were identified. Taken together, these data indicate that phages, as biologicals, may require some manner of protection (e.g., microencapsulation) to remain viable under various physiological and manufacturing conditions. In addition, based on its ability to effectively lyse diverse Salmonella serovars, phage vB_SalM-SJ2 could be further developed as an important biocontrol agent in various aspects of food production when the exact serovar or strain of contaminating Salmonella is not yet known.
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Hong
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: M
authors.initials: M
authors.lastname: Fealey
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: A
authors.initials: A
authors.lastname: Singh
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: K
authors.initials: K
authors.lastname: Walton
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: C
authors.initials: C
authors.lastname: Martin
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: N J
authors.initials: NJ
authors.lastname: Harman
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: J
authors.initials: J
authors.lastname: Mahlie
authors.affiliation: Department of Animal Sciences, Purdue University, West Lafayette, Indiana 47907, USA. pebner@purdue.edu.
authors.forename: P D
authors.initials: PD
authors.lastname: Ebner
mesh_terms: D000818:Animals; D016679:Genome, Viral; D012475:Salmonella / Q000254:growth & development / Q000821:virology*; D012481:Salmonella Infections, Animal / Q000382:microbiology / Q000628:therapy; D012483:Salmonella Phages / Q000235:genetics* / Q000502:physiology; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology / Q000628:therapy; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D014764:Viral Proteins