Widely distributed lysogeny in probiotic lactobacilli represents a potentially high risk for the fermentative dairy industry

►25 out of 30 strains of Lactobacillus of the casei group tested harboured prophages. ►Commercial probiotic lactobacilli usually comprise highly related lysogeny strains. ►The same or different prophages can be present in highly related probiotic strains. ►Mitomycin C lead to the release of 2 new virulent phages in probiotic lactobacilli.