Seleção de bactérias láticas de equinos com potencial probiótico para uso como promotor de crescimento ou adjuvante imunológico

Abstract

The use of food additives in animals diet is one of the techniques applied with significant results to improve production indices. Probiotics, which are beneficial to the health of the host and do not leave residues in animal products and do not promote drug resistance, are highlighted among the additives used in animal production. In this context, the present study aimed to characterize in vitro and in vivo lactic acid bacteria isolated from the feces of young foals for use as probiotics in food supplementats, growth promoters or immune adjuvants. Thirty-three bacteria of the genera Lactobacillus, Weissella, Pediococcus, and Enterococcus were tested in vitro in order to characterize and select potential probiotic strains. Some of these bacteria were stomach low pH resistant and about 30% showed mild or moderate growth inhibition by bile salts. Potential for adhesion to the intestinal epithelium surface was assessed indirectly from the ability shown by the bacteria to associate with nonpolar organic solvents. We observed that 40% of the tested isolates showed high or moderate cell surface hydrophobicity. Some bacterial strains showed strong antagonistic activity against almost all bacterial pathogens tested. All of the strains showed similar resistance/susceptibility patterns to antimicrobials used in human and animal therapy, do not having any tranferable resistance marker. The Pediococcus pentosaceus strain 40 and the Weissella confusa strain 1 showed better results in this in vitro probiotic functional characterization tests and they were chosen for the in vivo tests in mouse model of typhoid fever by infection with Salmonella enterica serovar Typhimurium. The safety of these two strains of lactic acid bacteria was demonstrated by the supplementation of mice for 10 consecutive days, which caused no increase in liver and spleen indexes, nor the death of any mice. However, these bacterial treatments did not promote an increase in the survival of those animals experimentally infected with S. Typhimurium enteropathogen. Quantification of relative mRNA levels of genes encoding the cytokines tumor necrosis factor alpha (TNFA), interferon gamma (IFNG), transforming growth factor beta (TGFB1) and interleukin 6 (IL6) and 10 (IL10). Testing, after 1, 4, 7 and 10 days of treatment with P. pentosaceus 40 revealed an inflammatory profile, inducing the expression of IFNG and a significant increase of TNFA expression, at 10 days after initiation of treatment. Therefore, the strains W. confusa 1 and P. pentosaceus 40 strains were considered safe, but they did not appear as an appropriate therapy against infection by S. Typhimurium. By inducing an inflammatory cytokine expression profile, it is possible that the P. pentosaceus 40 strain may serve as a vaccines immune adjuvant or confer some protection against major viral infections. Regarding the W. confusa 1, it is necessary to do the same cytokine induction profile analysis. However, the other in vivo results were very similar to P. pentosaceus 40. It is important to emphasize the need for in vivo tests to be performed on bacterial candidates for probiotics before they are used extensively in animal and human therapies. As the present study demonstrates, their effects will not always be beneficial against all kinds.