Objectives: Our group has concerned itself with the study of the effect of probiotics on the resistance to infections using experimental models. Here, we will focus on evidence that the UFV-H2b20 strain of Lactobacillus delbrueckii var. bulgaricus may be considered a probiotic and has protective effects on mice against a variety of bacterial infections.
Methods: Germ-free, monoassociated, and conventional mice were used. Mice were treated with probiotics and challenged with Escherichia coli, Salmonella enterica serovar Typhimurium, or Listeria monocytogenes, and the outcome of infection was measured as mortality, quantification of bacteria in target organs, and systemic of local cytokine production.
Results: L. delbrueckii increased clearance of E. coli and production of systemic inflammatory cytokines. This strain also protected monoassociated and conventional mice against infection with S. enterica serovar Typhimurium. Finally, monoassociated mice were more resistant to L. monocytogenes as measured by mortality and the number of bacteria in spleen and liver. In addition, monoassociated mice challenged with L. monocytogenes showed increased production of inflammatory cytokines (interferon-gamma and tumor necrosis factor-alpha) and nitric oxide. Interestingly, interleukin-10 levels were not altered by monoassociation or infection.
Conclusions: L. delbrueckii UFV-H2b20 protects mice against infection, apparently by eliciting the up-regulation of production of inflammatory cytokines.