Physiological Profiling of Lytic Bacteriophages and their Efficiency against Salmonella Enteritidis on Chicken Breast Cuts
Physiological Profiling of Lytic Bacteriophages and their Efficiency against Salmonella Enteritidis on Chicken Breast Cuts
Aleena Kokab1, Ali Ahmad Sheikh1*, Masood Rabbani1, Wasim Shehzad2, Muhammad Ilyas Riaz1, Sohail Raza1 and Rida Haroon Durrani1
ABSTRACT
Worldwide, antibiotic-resistant Salmonella Enteritidis being accountable for major foodborne Salmonella outbreaks, is a significant concern for public health and the agro-food sector. The use of bacteriophages, as a potential replacement, for antibiotics and as food antimicrobial agents to potentially target foodborne pathogens is gaining augmented attention. This study’s goal was to isolate and physiologically characterize lytic bacteriophages against Enteritidis, and to ascertain their efficacy in modulating bacterial population on chicken breast cuts in the form of a phage cocktail. Out of 17 isolated bacteriophages, three bacteriophages (SEPL01, SEPL13, SEPL20) exhibited maximum lytic potential and broad lytic spectrum. Transmission electron microscopy analysis classified SEPL01 as a Siphovirus and SEPL13 and SEPL20 as Myoviruses. In liquid culture, phage virulence activity was rapid and high at a high (100) multiplicity of infection with phage SEPL01 depicting the best activity among all. Compared to the solophage suspensions at high MOI, the phage cocktail comprising all three phages did not let the bacteria regrow until 24 h overcoming bacterial resistance. All the three bacteriophages demonstrated a broad host range within the genus Salmonella (Enteritidis, Typhimurium, Gallinarum, and Pullorum) embracing 100 percent activity with no heterologous activity against non-Salmonella serotypes tested. Latent time period of 15, 15, and 20 min was documented for SEPL01, SEPL13, and SEPL20, respectively, with an average burst size of 110, 32, and 63 PFU CFU-1, respectively. All the three bacteriophages were tolerant of temperature range 4°C-70°C and pH between 3-12, thus providing a broader window of their application throughout the food chain. On chicken breast cuts, phage mix efficiently supported sustained (3 days) bacterial reduction of 1.47 log units and 2.72 log units at MOI 100 and 10,000, respectively with greater MOI providing greater reduction. For standardizing the use of bacteriophages, physiological characterization is a crucial constraint. Owing to the strong lytic regime and spectrum, bacteriophages proved to be ideal for their use as an alternative or addition to conventional antimicrobials used in the food industry.
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