Protective effect of Lactobacillus sakei 2a against experimental challenge with Listeria monocytogenes in gnotobiotic mice

Abstract

Aim: Lactobacillus sakei 2a isolated from sausage and presenting an in vitro antagonistic activity against Listeria monocytogenes Scott A was tested for a protective effect in mice experimentally challenged with the enterobacteria. Methods and Results: In the experimental group, germ-free mice (n = 24) were inoculated intragastrically with 0·1 ml of a suspension containing 108 colony forming units (CFU) of Lact. sakei and 4 days later the animals were challenged intragastrically with 0·1 ml of a suspension containing 108 CFU of L. monocytogenes. Control group (n = 24) was only inoculated with the bacterial pathogen. Faecal counts showed that L. monocytogenes reached similar population levels (109 CFU g−1 of contents) in both the groups. Animals in the control group showed lower (P = 0·0004) survival frequency (58·3%) when compared with the experimental one (100%). Anatomopathological examination confirmed the mortality data. Conclusions: Lactobacillus sakei 2a can survive in the mammal digestive tract where showed a protective effect against L. monocytogenes. This phenomenon was not due to an antagonistic activity. Significance and Impact of the Study: Use of Lact. sakei 2a as a meat starter could inhibit not only L. monocytogenes growth in the fermented product but also pathogen virulence in the gastrointestinal tract.