Characterization of a Diverse Collection of Salmonella Phages Isolated from Tennessee Wastewater
Daniel W. Bryan 1*, Lauren K. Hudson 1, Jia Wang 1, Thomas G. Denes 1
- University of Tennessee Institute of Agriculture
Salmonella enterica is one of the most prevalent bacterial foodborne pathogens. As with other pathogens, there has been a concerning trend of increasing prevalence of antibiotic resistant isolates, including multi-drug resistant strains from both human outbreaks and in the food production environment. Salmonella bacteriophages are currently used in biocontrol applications and have potential for use as therapeutics. For the development of effective bacteriophage applications, diverse collections of well-characterized bacteriophages that are active against a broad range of target bacteria and that contain phages with both narrow and broad host ranges is an essential resource. To explore the diversity of phages present in wastewater effluent in eastern Tennessee and develop a collection of eastern Tennessee S. enterica phages for future use, samples were enriched, isolated, and purified from a collection of 24 Salmonella host isolates. From these isolates, ten phages were selected for further characterization. Morphology was determined with transmission electron microscopy, host ranges were characterized using an efficiency of plaquing assay, and comparative genomic analysis was performed to determine taxonomy. The characterized phages belong to the three major bacteriophage morphotypes (three myoviruses, two podoviruses, and five siphoviruses) Five different genera (Ithacavirus, Gelderlandvirus, Kuttervirus, Tlsvirus, and Epseptimavirus) are represented within these phages, with two belonging to established species, and eight belonging to novel species. When evaluated by efficiency of plaquing assay, these ten phages showed activity against 23 out of 24 Salmonella serovars, with host ranges varying from a single host to half of all tested serovars. Additionally, two phages displayed polyvalent activity against both Salmonella isolates and the lab strain E.coli B. The phages described here illustrate the diversity of S. enterica phages present in wastewater effluent and provide a collection of characterized phages from eastern Tennessee that may be of use in future phage-based applications targeting S. enterica.