CONICET | Buscador de Institutos y Recursos Humanos

Salmonella produces infections of different nature and severity which depend of many factors including the Salmonella serovar involved, strain virulence, infective dose, host animal species, age and immune status of the host. The treatments against Salmonella infections rely on supportive and antibiotic therapy to eliminate the pathogen, but the development of resistance by Salmonella to the most commonly used antimicrobials, limits its efficacy. Other disadvantages of antibiotic treatments are that they can lead to acute diarrhea (antimicrobials normally induce an imbalance of intestinal bacterial flora) and may produce chronic toxicity. Considering this undesired consequences of antibiotics and because at the present there are no effective oral vaccines which protect against salmonellosis, scientists have been searching for alternative methods to control enteric infections. At the present, probiotics are proposed as an attractive possibility to attend this concern. Probiotic are live microorganisms, which when administered in adequate amounts confer a health benefit on the host. In vitro and in vivo studies showed the effectiveness of probiotic administration in the prevention or in the treatment against Salmonella infection. There are several mechanisms by which probiotic strains might exert their effects. They include non immune mechanism (stabilization of the gut mucosal barrier, competition for adhesion, secretion of antimicrobial substances, etc) and the modulation of the mucosal and systemic immune responses. These mechanisms are species and/or strain specific. There are also evidences that in some cases, a mix of probiotic strains can be more useful than each strain alone against this infection. In addition, the presence of one or more probiotic strains in a fermented product can improve the beneficial properties of the probiotic strains involved. Although, the major part of the researches were performed in animal models through in vivo assays or by in vitro studies using human cell lines, some studies carried out in humans to verify the probiotic effects were also done. We studied the protective effect of Lactobacillus casei CRL 431 in the protection of Salmonella enterica serovar Typhimurium (S. Typhimurium), and the mechanisms involved in such protection .We determined that L. casei CRL 431 protects mice against S. Typhimurium infection. The continuous administration (before and after challenge with the pathogen) of the probiotic strain induced the best protection, with an increase in the levels of anti- Salmonella specifi IgA, phagocytic activity of peritoneal and Peyer patches macrophages, diminution in the mieloperoxidase activity at intestinal level and decreases in the release of inflammatory cytokines, with an enhance in the expression of Toll-like receptors (TLR) as a way to regulate the inflammatory process induced by the pathogen. We also demonstrated the importance of the activation of the intestinal epithelial cell (IEC). The administration of L. casei induces an earlier response of IECs against S. Typhimurium, by incrementing IL-6 levels necessary for clonal expansion of B-cells and specific anti-Salmonella s-IgA secretion. We also determined an increase in the secretion of MCP after probiotic administration, which is necessary for the recruitment of macrophages that limits S. Typhimurium dissemination. We demonstrated that the main mechanisms in the control of S. Typhimurium infection mediated by the probiotic strain L casei CRL 431 is exerted by an increase of the intestinal barrier, with increases of the total IgA, the TLR expression, and the release of cytokines by de IEC, and by an enhance in the innate immunity through the enhancement of the phagocytic activity of macrophages from Peyer patches, spleen and peritoneum and by the cytokine production from the gut associated immune cells. The adaptive immunity plays a secondary role and it is only mediated by specific IgA antibody. The main effect of this probiotic is to avoid the pathogen dissemination from the intestine to deep tissues. Nevertheless, is of critical importance to perform more clinical trials in humans to validate the results obtained with each specific probiotic strain or probiotic product. There are several mechanisms by which probiotic strains might exert their effects. They include non immune mechanism (stabilization of the gut mucosal barrier, competition for adhesion, secretion of antimicrobial substances, etc) and the modulation of the mucosal and systemic immune responses. These mechanisms are species and/or strain specific. There are also evidences that in some cases, a mix of probiotic strains can be more useful than each strain alone against this infection. In addition, the presence of one or more probiotic strains in a fermented product can improve the beneficial properties of the probiotic strains involved. Although, the major part of the researches were performed in animal models through in vivo assays or by in vitro studies using human cell lines, some studies carried out in humans to verify the probiotic effects were also done. We studied the protective effect of Lactobacillus casei CRL 431 in the protection of Salmonella enterica serovar Typhimurium (S. Typhimurium), and the mechanisms involved in such protection .We determined that L. casei CRL 431 protects mice against S. Typhimurium infection. The continuous administration (before and after challenge with the pathogen) of the probiotic strain induced the best protection, with an increase in the levels of anti- Salmonella specifi IgA, phagocytic activity of peritoneal and Peyer patches macrophages, diminution in the mieloperoxidase activity at intestinal level and decreases in the release of inflammatory cytokines, with an enhance in the expression of Toll-like receptors (TLR) as a way to regulate the inflammatory process induced by the pathogen. We also demonstrated the importance of the activation of the intestinal epithelial cell (IEC). The administration of L. casei induces an earlier response of IECs against S. Typhimurium, by incrementing IL-6 levels necessary for clonal expansion of B-cells and specific anti-Salmonella s-IgA secretion. We also determined an increase in the secretion of MCP after probiotic administration, which is necessary for the recruitment of macrophages that limits S. Typhimurium dissemination. We demonstrated that the main mechanisms in the control of S. Typhimurium infection mediated by the probiotic strain L casei CRL 431 is exerted by an increase of the intestinal barrier, with increases of the total IgA, the TLR expression, and the release of cytokines by de IEC, and by an enhance in the innate immunity through the enhancement of the phagocytic activity of macrophages from Peyer patches, spleen and peritoneum and by the cytokine production from the gut associated immune cells. The adaptive immunity plays a secondary role and it is only mediated by specific IgA antibody. The main effect of this probiotic is to avoid the pathogen dissemination from the intestine to deep tissues. Nevertheless, is of critical importance to perform more clinical trials in humans to validate the results obtained with each specific probiotic strain or probiotic product. We studied the protective effect of Lactobacillus casei CRL 431 in the protection of Salmonella enterica serovar Typhimurium (S. Typhimurium), and the mechanisms involved in such protection .We determined that L. casei CRL 431 protects mice against S. Typhimurium infection. The continuous administration (before and after challenge with the pathogen) of the probiotic strain induced the best protection, with an increase in the levels of anti- Salmonella specifi IgA, phagocytic activity of peritoneal and Peyer patches macrophages, diminution in the mieloperoxidase activity at intestinal level and decreases in the release of inflammatory cytokines, with an enhance in the expression of Toll-like receptors (TLR) as a way to regulate the inflammatory process induced by the pathogen. We also demonstrated the importance of the activation of the intestinal epithelial cell (IEC). The administration of L. casei induces an earlier response of IECs against S. Typhimurium, by incrementing IL-6 levels necessary for clonal expansion of B-cells and specific anti-Salmonella s-IgA secretion. We also determined an increase in the secretion of MCP after probiotic administration, which is necessary for the recruitment of macrophages that limits S. Typhimurium dissemination. We demonstrated that the main mechanisms in the control of S. Typhimurium infection mediated by the probiotic strain L casei CRL 431 is exerted by an increase of the intestinal barrier, with increases of the total IgA, the TLR expression, and the release of cytokines by de IEC, and by an enhance in the innate immunity through the enhancement of the phagocytic activity of macrophages from Peyer patches, spleen and peritoneum and by the cytokine production from the gut associated immune cells. The adaptive immunity plays a secondary role and it is only mediated by specific IgA antibody. The main effect of this probiotic is to avoid the pathogen dissemination from the intestine to deep tissues. Nevertheless, is of critical importance to perform more clinical trials in humans to validate the results obtained with each specific probiotic strain or probiotic product. We demonstrated that the main mechanisms in the control of S. Typhimurium infection mediated by the probiotic strain L casei CRL 431 is exerted by an increase of the intestinal barrier, with increases of the total IgA, the TLR expression, and the release of cytokines by de IEC, and by an enhance in the innate immunity through the enhancement of the phagocytic activity of macrophages from Peyer patches, spleen and peritoneum and by the cytokine production from the gut associated immune cells. The adaptive immunity plays a secondary role and it is only mediated by specific IgA antibody. The main effect of this probiotic is to avoid the pathogen dissemination from the intestine to deep tissues. Nevertheless, is of critical importance to perform more clinical trials in humans to validate the results obtained with each specific probiotic strain or probiotic product.