A P60 mutant of Listeria monocytogenes is impaired in its ability to cause infection in intragastrically inoculated mice

A spontaneous P60 mutant of Listeria monocytogenes was less able to cause systemic infection in A/J mice, following intragastric inoculation, than the parental wild type strain (SLCC 5764, serotype 1/2a). Significantly fewer CFU were recovered from internal organs (spleen, liver, gall bladder) and from the cecum of mice inoculated intragastrically with the P60 mutant than mice inoculated with wild type L. monocytogenes. The P60 mutant also exhibited a diminished ability to invade and multiply within Caco-2 intestinal epithelial cells. These findings indicate that P60 is required for maximal virulence of L. monocytogenes in the gastrointestinal tract of mice.