The effect of Saccharomyces boulardii on the immune system was evaluated, comparing germ‐free Swiss/NIH mice monoassociated with the probiotic with germ‐free mice. Saccharomyces boulardii colonized the gut of germ‐free mice and survived the gastrointestinal conditions. An increase in sIgA production, both total and anti‐S. boulardii, was observed in the intestinal contents of monoassociated mice when compared with germ‐free controls. The number of Küpffer cells was significantly higher in monoassociated mice than in germ‐free controls. In S. boulardii‐monoassociated mice, clearance of Escherichia coli B41 was higher than in germ‐free controls. TNF‐α, IFN‐γ and IL‐12 serum levels were higher at earlier time points in monoassociated mice when compared with germ‐free mice. These results show that the yeast S. boulardii modulates the host immune responses. This effect may be of interest for improving the resistance to enteropathogenic bacterial infections.

Saccharomyces boulardii was shown to be capable of inhibiting multiplication of enteropathogenic bacteria in vitro and is currently used for its anti-diarrhoea properties. We studied the capacity of this yeast to antagonize Salmonella typhimurium and Shigella flexneri in the intestinal tract of conventional or gnotobiotic NMRI mice. Conventional animals were given daily 10 mg doses of S. boulardii, whereas germ-free animals were given a single 10 mg dose. Both groups were challenged orally 5 d later with the pathogenic bacteria (10(8) or 10(2) viable cells, respectively). Control groups were treated with saline instead of S. boulardii. Mortality and/or histopathological data showed a protective effect against the pathogenic bacteria in yeast-treated mice. Saccharomyces boulardii colonized the digestive tract of gnotobiotic mice and the number of viable cells ranged around 10(10) g-1 of faeces. In experimental and control gnotobiotic animals, Salm. typhimurium and Sh. flexneri became rapidly established at a level of about 10(10) viable cells g-1 of faeces and remained at high levels until the animals died or were sacrificed. The protection against Salm. typhimurium and Sh. flexneri obtained in conventional and/or gnotobiotic mice previously associated with S. boulardii is not due to the reduction of the bacterial populations in the intestines.

Previous results in the laboratory of the authors showed that Saccharomyces cerevisiae strain 905, isolated during 'cachaç a' production, was able to colonize and survive in the gastrointestinal tract of germ-free and conventional mice, and to protect these animals against oral challenge with Salmonella enterica serotype Typhimurium or Clostridium difficile. In the present work, the effects of S. cerevisiae 905 on the translocation of Salm. Typhimurium (mesenteric lymph nodes, Peyer's patches, spleen, liver) as well as on the immune system (number of Kü pffer cells, immunoglobulin production, clearance of Escherichia coli B 41 ) were evaluated in gnotobiotic and/or conventional mice. The treatment with the yeast reduced significantly the translocation of Salm. Typhimurium to liver in gnotobiotic animals and to all the organs tested in conventional mice. The number of Kü pffer cells per 100 hepatocytes in liver was significantly higher (P<0.05) in yeast mono-associated mice (52.9±15.7) than in germ-free controls (38.1±9.0). Probably as a consequence, clearance of E. coli B 41 from the bloodstream was more efficient in yeast mono-associated animals when compared to germ-free mice. Higher levels (P<0.05) of secretory IgA in intestinal content and of IgA and IgM in serum were observed in yeast mono-associated mice when compared to germ-free group. Concluding, the protection against pathogenic bacteria observed in a previous study was probably due to a modulation of both local and systemic immunity of mice treated with S. cerevisiae 905. INTRODUCTIONProbiotics are defined as live micro-organisms that when administered in adequate amounts confer a health benefit to the host (Food and Agriculture Organization of the United Nations & World Health Organization, 2002). These microorganisms are widely used in pharmaceutical preparations and fermented dairy products. Lactobacilli and Bifidobacteria are typically found in probiotic products for humans, as well as some yeasts such as Saccharomyces boulardii.S. boulardii, a non-pathogenic yeast, was isolated from lychee fruit in Indochina and grows at the unusually high temperature of 37 uC (McFarland & Bernasconi, 1993). It has been used for the treatment of different types of diarrhoeal diseases, such as antibiotic-associated diarrhoea (Bartlett, 1992;McFarland et al., 1995;Surawicz, 2003), Clostridium difficile-associated intestinal disease (Elmer et al., 1999;Surawicz et al., 2000;Surawicz, 2003), traveller's diarrhoea (Scarpignato & Rampal, 1995) and diarrhoea in HIV-infected patients (Born et al., 1993).Many mechanisms of action have been proposed to explain S. boulardii protection and they have been summarized by et al., 2004). This leads to the question whether other strains of Saccharomyces, as well as S. boulardii, possess biotherapeutic properties. Brazil is well known for its rich biodiversity in terms of animal, vegetal and microbial species, and yeast with probiotic properties certainly could be screened from Brazilian environmental and agroindustrial sources. ...

Lactobacillus delbrueckii UFV-H2b20 has been shown to increase clearance of bacteria injected into the blood of germ-free mice. Moreover, it induces the production of type 1 cytokines by human peripheral mononuclear cells. The objective of the present study was to investigate the production of inflammatory cytokines [interleukin-12 (IL-12 p40), tumor necrosis factor-α (TNF-α), and interferon-γ (IFN-γ)] triggered in vitro by live, heat-killed or lysozyme-treated L. delbrueckii UFV-H2b20 and in vivo by a live preparation. Germ-free, L. delbrueckii-monoassociated and lipopolysaccharide (LPS)-resistant C3H/HeJ mice were used as experimental models. UFV-H2b20 induced the production of IL-12 p40 and TNF-α by peritoneal cells and IFN-γ by spleen cells from germ-free or monoassociated Swiss/NIH mice and LPS-hyporesponsive mice (around 40 ng/mL for IL-12 p40, 200 pg/mL for TNF-α and 10 ng/mL for IFN-γ). Heat treatment of L. delbrueckii did not affect the production of these cytokines. Lysozyme treatment decreased IL-12 p40 production by peritoneal cells from C3H/HeJ mice, but did not affect TNF-α production by these cells or IFN-γ production by spleen cells from the same mouse strain. TNF-α production by peritoneal cells from Swiss/NIH L. delbrueckii-monoassociated mice was inhibited by lysozyme treatment. When testing IL-12 p40 and IFN-γ levels in sera from germ-free or monoassociated Swiss/NIH mice systemically challenged with Escherichia coli we observed that IL-12 p40 was produced at marginally higher levels by monoassociated mice than by germ-free mice (40 vs 60 ng/mL), but IFN-γ was produced earlier and at higher levels by monoassociated mice (monoassociated 4 and 14 ng/mL 4 and 8 h after infection, germfree 0 and 7.5 ng/mL at the same times). These results show that L. delbrueckii UFV-H2b20 stimulates the production of type 1 cytokines in vitro and in vivo, therefore suggesting that L. delbrueckii might have adjuvant properties in infection in which these cytokines play a major role.