Protective effect of Lactobacillus sakei 2a against experimental challenge with Listeria monocytogenes in gnotobiotic mice.
ABSTRACT 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.
In the experimental group, germ-free mice (n = 24) were inoculated intragastrically with 0.1 ml of a suspension containing 10(8) colony forming units (CFU) of Lact. sakei and 4 days later the animals were challenged intragastrically with 0.1 ml of a suspension containing 10(8) 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 (10(9) 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.
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.
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.
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ABSTRACT: We have observed that antagonisms occur between isogenic strains of Escherichia coli associated with gnotobiotic mice. The strains differed in the carriage of plasmids or in chromosomal mutations. The plasmid-free strains, in general, inhibited the establishment of plasmid-bearing strains in the gastrointestinal tract of mice. The outcome of the interactions between isogenic pairs, however, depended on the order in which the strains were introduced into the mice. Maintaining the bacterial strains in monoassociation with gnotobiotic mice resulted in the "adaptation" of the bacteria to their host. Thus, in all cases, "adapted" strains became the dominant population in the feces of mice, regardless of whether the adapted strains was introduced into mice before or after its isogenic partner which had been cultured in vitro. The ecological advantage disappeared when the adapted strain was cultured in broth. Ultrastructural differences in cell morphology were observed between strains maintained in vivo and in vitro.Infection and Immunity 01/1982; 34(3):957-69. · 4.07 Impact Factor
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ABSTRACT: Lactobacilli are nonpathogenic gram-positive inhabitants of microflora. At least some Lactobacillus strains have been postulated to have health beneficial effects, such as the stimulation of the immune system. Here we examined the stimulatory effects of lactobacilli on mouse immune cells. All six heat-killed Lactobacillus strains examined induced the secretion of tumor necrosis factor alpha (TNF-alpha) from mouse splenic mononuclear cells, albeit to various degrees. When fractionated subcellular fractions of Lactobacillus casei were tested for NF-kappaB activation and TNF-alpha production in RAW264.7, a mouse macrophage cell line, the activity was found to be as follows: protoplast > cell wall > polysaccharide-peptidoglycan complex. Both crude extracts and purified lipoteichoic acids (LTAs) from two Lactobacillus strains, L. casei and L. fermentum, significantly induced TNF-alpha secretion from RAW264.7 cells and splenocytes of C57BL/6, C3H/HeN, and C3H/HeJ mice but not from splenocytes of C57BL/6 TLR2(-/-) mice. Lactobacillus LTA induced activation of c-Jun N-terminal kinase activation in RAW264.7 cells. Furthermore, in HEK293T cells transected with a combination of CD14 and Toll-like receptor 2 (TLR2), NF-kappaB was activated in response to Lactobacillus LTA. Taken together, these data suggest that LTAs from lactobacilli elicit proinflammatory activities through TLR2.Clinical and Diagnostic Laboratory Immunology 03/2003; 10(2):259-66. · 2.51 Impact Factor
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ABSTRACT: We evaluated the ability of Lactobacillus delbrueckii UFV H2b20, a probiotic candidate, to stimulate the production of inflammatory cytokines and to induce macrophage activation and Th1 differentiation in peripheral blood mononuclear cells (PBMC) from healthy volunteers. Our results show that PBMC stimulated with heat-killed Lact. delbrueckii produced elevated levels of IL-12, IFN-gamma and TNF-alpha but no IL-10. IFN-gamma production was IL-12 dependent with NK cells as the main source. Furthermore, PBMC infected with Leishmania amazonensis presented elevated microbicidal activity when co-incubated with Lact. delbrueckii. Finally, Lact. delbrueckii was capable of inducing in vitro differentiation of L. amazonensis-specific Th1 cells. These findings suggest that this probiotic may be used as an adjuvant in vaccination protocols.Frontiers in Bioscience 02/2007; 12:1300-7. · 3.29 Impact Factor