Physicochemical characterization of ten newly isolated phages against the foodborne pathogen Shigella flexneri

Abstract

Ten bacteriophages with lytic activity against Shigella flexneri were tested for their resistance to physicochemical conditions found in food matrices. Phage viability and activity were evaluated at different temperatures, pH values, and NaCl concentrations. In addition, challenge tests with each individual phage against ATCC 12022 were conducted to evaluate their use as biocontrol agents. Although phages showed high resistance up to 60°C, Shi30, Shi33, and Shi93 showed higher thermal resistance (70°C). The ten phages endured pH treatments, being more resistant to alkaline conditions. The NaCl concentrations evaluated showed no significant influence on phage counts. Furthermore, challenge tests against ATCC 12022 resulted in significant CFU ml−1 reductions. The results showed that the phages evaluated were resistant to a wide range of temperatures and pH and to all the concentrations of NaCl tested. Therefore, the phages evaluated in this study could potentially be used with biocontrol purposes in various food matrices prior further characterization. Novelty impact statement: Ten newly isolated phages against the foodborne pathogen Shigella flexneri remained viable after different physicochemical treatments. Furthermore, their activity was maintained after thermal and chemical treatments. Also, the ten phages were effective against pathogenic Shigella flexneri strains in challenge tests.