BackgroundDiarrheal infections caused by Salmonella, are one of the major causes of childhood morbidity and mortality in developing countries. Salmonella causes various diseases that range from mild gastroenteritis to enteric fever, depending on the serovar involved, infective dose, species, age and immune status of the host. Probiotics are proposed as an attractive alternative possibility in the prevention against this pathogen infection. Previously we demonstrated that continuous Lactobacillus casei CRL 431 administration to BALB/c mice before and after challenge with Salmonella enterica serovar Typhimurium (S. Typhimurium) decreased the severity of Salmonella infection. The aim of the present work was to deep into the knowledge about how this probiotic bacterium exerts its effect, by assessing its impact on the expression and secretion of pro-inflammatory (TNFα, IFNγ) and anti-inflammatory (IL-10) cytokines in the inductor and effector sites of the gut immune response, and analyzing toll-like receptor (TLR2, TLR4, TLR5 and TLR9) expressions in both healthy and infected mice.ResultsProbiotic administration to healthy mice increased the expression of TLR2, TLR4 and TLR9 and improved the production and secretion of TNFα, IFNγ and IL-10 in the inductor sites of the gut immune response (Peyer's patches). Post infection, the continuous probiotic administration, before and after Salmonella challenge, protected the host by modulating the inflammatory response, mainly in the immune effector site of the gut, decreasing TNFα and increasing IFNγ, IL-6 and IL-10 production in the lamina propria of the small intestine.ConclusionsThe oral administration of L. casei CRL 431 induces variations in the cytokine profile and in the TLRs expression previous and also after the challenge with S. Typhimurium. These changes show some of the immune mechanisms implicated in the protective effect of this probiotic strain against S. Typhimurium, providing an alternative way to reduce the severity of the infection.

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Aims: To investigate the immunoprotective ability of three Lactobacilli strains against Salmonella enterica serovar Typhimurium in a mouse model. To identify the probiotic properties involved in the protection against infection caused by this pathogen. Methods and Results: The immunomodulatory effect of three different lactobacilli strains: Lactobacillus (Lact.) casei CRL 431 (probiotic bacterium), Lact. delbrueckii subsp. bulgaricus CRL 423 (Lact. bulgaricus) and Lact. acidophilus CRL 730 was compared using a mouse model of Salmonella infection. Lactobacillus casei continuous administration improved animal survival, diminished pathogen spreading outside the intestine, attenuated the intestinal inflammation, modulated cytokine profile previous and postinfection and increased the expression and secretion of IgA in the gut. Additionally, the administration of this lactobacilli increased peritoneal, Peyer's patches and spleen macrophages' phagocytic activity in healthy mice and monocyte chemotactic protein (MCP-1) released by intestinal epithelial cells in an in vitro assay. Although Lact. acidophilus increased the number of IgA-secreting cells previous and postinfection, and Lact. bulgaricus increased MCP-1 released by intestinal epithelial cells and the phagocytic activity of macrophages, these effects alone were not enough to confer protection against Salmonella Typhimurium infection in mouse. Conclusions: Probiotic strain Lact. casei CRL 431 was the one that induced protection against Salmonella, by increasing the intestinal barrier function and by decreasing the local inflammatory response. Significance and Impact of the Study: Salmonella spp. constitutes an important agent of foodborne diseases in the world. Not all lactobacilli, even with some immunostimulating properties at gut level, can protect against Salmonella infection. Lactobacillus casei CRL 431, a probiotic bacterium, could be useful as an oral mucosal adjuvant of the immune system to improve gut health, especially in the prevention or amelioration of Salmonella infections. We demonstrated that there is not a unique mechanism by which this protective effect was exerted.

Synthetic petroleum-based polymers and natural plant polymers have the disadvantage of restricted sources, in addition to the non-biodegradability of the former ones. In contrast, eco-sustainable microbial polysaccharides, of low-cost and standardized production, represent an alternative to address this situation. With a strong global market, they attracted worldwide attention because of their novel and unique physico-chemical properties as well as varied industrial applications, and many of them are promptly becoming economically competitive. Scleroglucan, a β-1,3-β-1,6-glucan secreted by Sclerotium fungi, exhibits high potential for commercialization and may show different branching frequency, side-chain length, and/or molecular weight depending on the producing strain or culture conditions. Water-solubility, viscosifying ability and wide stability over temperature, pH and salinity make scleroglucan useful for different biotechnological (enhanced oil recovery, food additives, drug delivery, cosmetic and pharmaceutical products, biocompatible materials, etc.), and biomedical (immunoceutical, antitumor, etc.) applications. It can be copiously produced at bioreactor scale under standardized conditions, where a high exopolysaccharide concentration normally governs the process optimization. Operative and nutritional conditions, as well as the incidence of scleroglucan downstream processing will be discussed in this chapter. The relevance of using standardized inocula from selected strains and experiences concerning the intricate scleroglucan scaling-up will be also herein outlined.