Core Lipopolysaccharide-Specific Phage SSU5 as an Auxiliary Component of a Phage Cocktail for Salmonella Biocontrol

Abstract

ABSTRACTSalmonellaspp. are among the major food-borne pathogens that cause mild diarrhea to severe bacteremia. The use of bacteriophages to control various food-borne pathogens, includingSalmonella, has emerged as a promising alternative to traditional chemotherapy. We isolated theSiphoviridaefamily phage SSU5, which can infect only rough strains ofSalmonella. The blocking of SSU5 adsorption by periodate treatment of hostSalmonellacells and spotting and adsorption assays with mutants that contain various truncations in their lipopolysaccharide (LPS) cores revealed that the outer core region of the LPS is a receptor of SSU5. SSU5 could infect O-antigen (O-Ag)-deficientSalmonellamutants that developed by challenging of O-Ag-specific phages, and consequently, it delayed the emergence of the phage-resistantSalmonellapopulation in broth culture when treated together with phages using O-Ag as a receptor. Therefore, these results suggested that phage SSU5 would be a promising auxiliary component of a phage cocktail to control rough strains ofSalmonella entericaserovar Typhimurium, which might emerge as resistant mutants upon infection by phages using O-Ag as a receptor.