ABSTRACT
We studied the ability of the probiotic organism Enterococcus faecium SF68 to antagonize Giardia intestinalis infection in mice. Oral feeding of E. faecium strain SF68 starting 7 d before inoculation with Giardia trophozoites significantly increased the production of specific anti-Giardia intestinal IgA and blood IgG. This humoral response was mirrored at the cellular level by an increased percentage of CD4(+) T cells in the Peyer's patches and in the spleens of SF68-fed mice. The improvement of specific immune responses in probiotic-fed mice was associated with a diminution in the number of active trophozoites in the small intestine as well as decreased shedding of fecal Giardia antigens (GSA65 protein). The ability of SF68 to stimulate the immune system at both mucosal and systemic levels highlights mechanisms by which this probiotic might antagonize pathogens in vivo. Taken together, the data demonstrate the strong potential of strain SF68 to prevent protozoa from causing intestinal infections.
Subject(s)
Enterococcus faecium/immunology , Giardia lamblia , Giardiasis/immunology , Probiotics/therapeutic use , Animals , Disease Models, Animal , Enterococcus faecium/isolation & purification , Feces/microbiology , Giardia lamblia/isolation & purification , MiceSubject(s)
Germ-Free Life/immunology , Immune System/immunology , Lactobacillus/immunology , Animals , Epithelium/immunology , Feces/microbiology , Immunoglobulins/analysis , Intestinal Mucosa/cytology , Intestinal Mucosa/immunology , Intestines/microbiology , Lactobacillus acidophilus/immunology , Lacticaseibacillus casei/immunology , Leukocyte Count , Lymphocyte Count , Mice , NeutrophilsABSTRACT
This study was undertaken to elucidate whether eating a fermented milk containing Lactobacillus acidophilus La1 and bifidobacteria could induce changes in intestinal flora and modulate the immune response in man. Volunteers consumed a fermented milk containing L. acidophilus La1 and bifidobacteria over a period of three weeks during which an attenuated Salmonella typhi Ty21a was administered to mimic an enteropathogenic infection. A control group ate no fermented foods but received the S. typhi Ty21a. Faecal flora analyses showed an increase in L. acidophilus and bifidobacterial counts during fermented milk intake. The specific serum IgA titre rise to S. typhi Ty21a in the test group was > 4-fold and significantly higher (P = 0.04) than in the control group. An increase in total serum IgA was also observed. These results indicate that lactic acid bacteria which can persist in the gastrointestinal tract can act as adjuvants to the humoral immune response.
