Utilizing the effectiveness of phage cocktail to combat Shigella and Salmonella infections and their polymicrobial biofilm control activity.

BACKGROUND: Shigella and Salmonella are major foodborne and waterborne pathogens responsible for acute gastrointestinal infections and significant global morbidity and mortality. Both species are capable of forming bacterial biofilms in the food processing industry, a key survival mechanism that significantly reduces the effectiveness of antibacterial drugs. The global rise in antimicrobial resistance (AMR) necessitates the urgent development of new strategies. Bacteriophages, particularly phage cocktails, provide a potential alternative because of their host specificity and ability to degrade biofilms. RESULTS: In this study, a new bacteriophage, Sspk23, infecting Shigella sonnei, was isolated from lake water and biologically characterized to assess its lytic activity and stability under varying conditions. Furthermore, this study investigates the effectiveness of a phage cocktail, including a newly isolated Sspk23 and two previously identified phages, Sfk20 and STWB21, against Shigella and Salmonella infections with a focus on its ability to combat single and polymicrobial infections. The biofilm removal potential of the phage cocktail was observed using Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM), and also quantitatively assessed in a microtiter plate. Cytotoxicity tests were conducted on human adherent epithelial cell line and macrophage cell line to confirm the safety of the phage and phage cocktail for therapeutic use. CONCLUSIONS: The findings demonstrate the possibility of a phage cocktail as a substitute for conventional antibiotics in controlling Shigella and Salmonella infections. Additionally, their capacity to destroy biofilms indicates potential applications in clinical therapies, environmental remediation, and food safety. Future studies will be focused on phage-antibiotic synergy optimization and in vivo validation to combat multidrug-resistant (MDR) bacteria.