Phage inactivation of foodborne Shigella on ready-to-eat spiced chicken

Shigellosis, also called bacillary dysentery, is an infectious disease caused by Shigella species, including Shigella flexneri, Shigella dysenteriae, Shigella sonnei, and Shigella boydii. Infection with S. flexneri can result in epidemics, and Shigella-contaminated food is often the source of infection, such as ready-to-eat spiced chicken and duck. Therefore, we investigated the ability of Shigella phages to inhibit pathogenic Shigella spp. in ready-to-eat spiced chicken. Food samples were inoculated with individual species (1 x 10(4) cfu/g) or a mixture (S. flexneri 2a, S. dysenteriae, and S. sonnei) to a total concentration of 3 x 10(4) cfu/g. Single phages or a phage cocktail were added thereafter (1 x 10(8) pfu/g or 3 x 10(8) pfu/g), respectively, and samples were incubated at 4 degrees C for 72 h. In general, the application of more phages (3 x 10(8) pfu/g) was the most effective treatment. Phages could reduce bacterial counts by up to 2 log(10)/g after 48 h incubation when treated with the cocktail, and after 72 h the host could not be detected. Similarly, the host in spiced chicken treated with single phage was also sharply reduced after 72 h incubation. The results suggest that an obligately virulent phage cocktail, such as S. flexneri, S. dysenteriae, and S. sonnei phages, can effectively reduce potential contamination of Shigella spp. in ready-to-eat chicken products.