This study was designed to evaluate the lytic activity of bacteriophage P22 against Salmonella Typhimurium ATCC 19585 (Salmonella Typhimurium P22) at various multiplicities of infections (MOIs), the susceptibility of preattached Salmonella cells against bacteriophage P22, and the effect of P22-mediated bacterial lysates (extracellular DNA) on the attachment ability of Listeria monocytogenes ATCC 7644 and enterohemorrhagic Escherichia coli ATCC 700927 to surfaces. The numbers of attached Salmonella Typhimurium P22 cells were effectively reduced to below the detection limit (1 log CFU/ml) at the fixed inoculum levels of 3 × 102 CFU/ml (MOI = 3.12) and 3 × 103 CFU/ml (MOI = 4.12) by bacteriophage P22. The attached Salmonella Typhimurium P22 cells remained more than 2 log CFU/ml, with increasing inoculum levels from 3 × 104 to 3 × 107 CFU/ml infected with 4 × 108 PFU/ml of P22. The number of preattached Salmonella Typhimurium P22 cells was noticeably reduced by 2.72 log in the presence of P22. The highest specific attachment ability values for Salmonella Typhimurium P22, Salmonella Typhimurium ATCC 23555 carrying P22 prophage (Salmonella Typhimurium P22+), L. monocytogenes, and enterohemorrhagic E. coli were 2.09, 1.06, 1.86, and 1.08, respectively, in the bacteriophage-mediated cell-free supernatants (CFS) containing high amounts of extracellular DNA. These results suggest that bacteriophages could potentially be used to effectively eliminate planktonic and preattached Salmonella Typhimurium P22 cells with increasing MOI. However, further research is needed to understand the role of bacteriophage-induced lysates in bacterial attachment, which can provide useful information for the therapeutic use of bacteriophage in the food system.

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