The evaluation of the impact of probiotics on host health could help to understand how they can be used in the prevention of diseases. On the basis of our previous studies andin vitroassays on PBMC and Caco-2 ccl20:luc reporter system presented in this work, the strainLactobacillus kefiriCIDCA 8348 was selected and administrated to healthy Swiss mice daily for 21 days. The probiotic treatment increased IgA in feces and reduced expression of proinflammatory mediators in Peyer Patches and mesenteric lymph nodes, where it also increased IL-10. In ileum IL-10, CXCL-1 and mucin 6 genes were upregulated; meanwhile in colon mucin 4 was induced whereas IFN-γ, GM-CSF, and IL-1βgenes were downregulated. Moreover, ileum and colon explants showed the anti-inflammatory effect ofL. kefirisince the LPS-induced increment of IL-6 and GM-CSF levels in control mice was significantly attenuated inL. kefiritreated mice. Regarding fecal microbiota, DGGE profiles allowed differentiation of experimental groups in two separated clusters. Quantitative PCR analysis of different bacterial groups revealed only significant changes inLactobacilluspopulation. In conclusion,L. kefiriis a good candidate to be used in gut inflammatory disorders.

Lactobacilli are generally regarded as safe; however, certain strains have been associated with cases of infection. Our workgroup has already assessed many functional properties ofLactobacillus kefiri, but parameters regarding safety must be studied before calling them probiotics. In this work, safety aspects and antimicrobial activity ofL. kefiristrains were studied. None of theL. kefiristrains tested causedα- orβ-hemolysis. All the strains were susceptible to tetracycline, clindamycin, streptomycin, ampicillin, erythromycin, kanamycin, and gentamicin; meanwhile, two strains were resistant to chloramphenicol. On the other hand, allL. kefiristrains were able to inhibit both Gram(+) and Gram(−) pathogens. Regarding thein vitroresults,L. kefiriCIDCA 8348 was selected to performin vivostudies. Mice treated daily with an oral dose of 10⁸CFU during 21 days showed no signs of pain, lethargy, dehydration, or diarrhea, and the histological studies were consistent with those findings. Moreover, no differences in proinflammatory cytokines secretion were observed between treated and control mice. No translocation of microorganisms to blood, spleen, or liver was observed. Regarding these findings,L. kefiriCIDCA 8348 is a microorganism isolated from a dairy product with a great potential as probiotic for human or animal use.

The effect of freeze-drying on viability and probiotic properties of a microbial mixture containing selected bacterial and yeast strains isolated from kefir grains (Lactobacillus kefir,Lactobacillus plantarum,Lactococcus lactis,Saccharomyces cerevisiaeandKluyveromyces marxianus) was studied. The microorganisms were selected according to their potentially probiotic propertiesin vitroalready reported. Two types of formulations were performed, a microbial mixture (MM) suspended in milk and a milk product fermented with MM (FMM). To test the effect of storage on viability of microorganisms, MM and FMM were freeze-dried and maintained at 4°C for six months. After 180 days of storage at 4°C, freeze-dried MM showed better survival rates for each strain than freeze-dried FMM. The addition of sugars (trehalose or sucrose) did not improve the survival rates of any of the microorganisms after freeze-drying. Freeze-drying did not affect the capacity of MM to inhibit growth ofShigella sonnei in vitro, since the co-incubation of this pathogen with freeze-dried MM produced a decrease of 2 log inShigellaviability. The safety of freeze-dried MM was tested in mice and non-translocation of microorganisms to liver or spleen was observed in BALB/c mice feedad libitumduring 7 or 20 days. To our knowledge, this is the first report about the effect of freeze-drying on viability,in vitroprobiotic properties and microbial translocation of a mixture containing different strains of both bacteria and yeasts isolated from kefir.