Probiotics possibly affect local and systemic immune reactions and maintain the intestinal immune homeostasis in healthy individuals and patients with diseases such as irritable bowel syndrome (IBS). In this single-center, blinded trial, we enrolled 40 individuals (20 patients with IBS and 20 healthy individuals) whose blood and fecal samples were collected before and after a 21-day administration of a product comprising Lactobacillus spp., larch arabinogalactan, and colostrum. The percentage of HLA-DR+ natural killer (NK) cells was higher in healthy individuals (p = 0.03) than in patients with IBS after product supplementation. In the fecal samples of patients with IBS, we observed a decline in IL-6, IFN-γ, TNF-α, and secretory IgA levels and, simultaneously, an increase in IL-10 and IL-17A levels after supplementation, although non-significant, whereas, in healthy individuals, we observed a significant decline in IL-6 and IFN-γ levels after supplementation (p < 0.001). Nevertheless, we observed a clinical improvement of symptoms in 65–75% of patients with IBS and the complete resolution of the initial symptoms in five of the 20 patients. We also observed a possible prophylactic effect by the inducing system antiviral impact accompanied by a trend for local immune tolerance in the gut in healthy individuals, where it is the desirable state.

Lactobacilli are considered important probiotics for the prevention of some infections. In this study, the antifungal effect of both cells and cell-free supernatants of twenty-three strains of lactobacilli were investigated against Candida albicans by co-aggregation, agar diffusion assay, agar spot assay and co-culture assay. In all cases, a fungistatic effect was recorded. In the agar diffusion assay and agar spot assay, an effect was established primarily for heterofermentative species via the production of lactic acid. The anti-Candida effect was higher with microbial suspension than with cultural supernatants in the co-culture assay. A strain-specific reduction in the yeast growth up to 28.9% in MRS broth and up to 17.1% in BHI broth was observed. Cells of Limosilactobacillus fermentum LLF-01 and Limosilactobacillus reuteri LLR-K67 showed the highest activity in both model systems. For all strains, a lower reduction up to 9.7% was recorded with cultural supernatants. L. fermentum LLF-01 showed the highest ability of co-aggregation (64.8%) with C. albicans, followed by Lactobacillus acidophilus LLA-01, Lactobacillus gasseri LLG-V74, Lactobacillus delbrueckii subsp. bulgaricus LLB-02 and two strains of Lactobacillus delbrueckii subsp. lactis LLL-14 and LLL-F18. The present study showed the potential of several strains of lactobacilli to affect the population of C. albicans in vitro. The combination of cultures with proved anti-Candida and co-aggregation activity in a probiotic formula may have a positive effect for the prevention of yeast overgrowth in the gut and hence for the suppression of candidiasis.