Seleção de bifidobactéria de origem humana para uso como probiótico em alimento funcional: avaliação do efeito protetor na infecção experimental com Salmonella enterica subsp. enterica sorovar Typhimurium

Abstract

The intestinal microbiota produces various beneficial health effects, and there is a growing interest in its modulation using probiotics. In the present study, we evaluated the potential of four species of probiotic bifidobacteria isolated from the feces of healthy children and identified for PCR Multiplex (Bifidobacterium longum 51A, Bifidobacterium breve 1101A, Bifidobacterium bifidum 1191A and Bifidobacterium pseudolongum 1622A). We studied the growth rate, aerotolerance, antagonistic activity against pathogens, antimicrobial susceptibility profile and hydrophobicity. Based on these parameters tested in vitro, B. longum 51A showed the best potential as candidate for probiotic use, presenting the greatest sensitivity to antimicrobials, the best growth rate and a large ability to produce antagonistic substances against various pathogenic microorganisms. Moreover, this strain colonized rapidly the gastrointestinal tract of germ-free mice, reaching high population levels in the feces of these animals. Treatment with yoghurt containing this strain had a local effect for the stimulation of IgA + cell proliferation in the small and large intestines and a protective effect against challenge with Salmonella enterica ser. Typhimurium, providing a 100% rate of survival in the animals fed yoghurt supplemented with fresh culture, despite the loss of viability and increase in sensitivity to simulated gastric resistance. Treatment of animals with pure culture of bifidobacteria also exerted a stimulation of the humoral response by higher levels of sIgA in intestinal contents and of IgM in serum and cellular stimulation by an increase in levels of mRNA for IL5 and reduction to Tnfa. However, it was not able to totally protect against infection by Salmonella. There was a small initial protection in the first days of infection, by stimulating the production of sIgA up to three days post challenge, which agrees with the slight delay in the time of death of the animals treated and the histopathological evaluation. After nine days of infection, the intestines and liver were better preserved in mice treated with the bifidobacteria. These results show that B. longum 51A has a potential to be used as probiotic. However, a better understanding of the mechanisms involved in the beneficial effects of this strain is necessary to optimize its use.