The influence of antibacterial and antioxidative probiotic lactobacilli on gut mucosa in a mouse model ofSalmonellainfection

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Abstract
The purpose of the present study was to test the ability of selected probiotic Lactobacillus spp. (with high antimicrobial and antioxidative potential in in vitro tests) to compete with invasive Salmonella enterica serovar Typhimurium infection and protect the gut mucosa against excessive oxidative stress during inflammatory tissue damage in a mouse model. In total 47 mice were divided into four groups. The control group was treated with either phosphate-buffered saline (PBS, group 1) or alternatively 0.5×108 CFU/ml of human intestinal lactobacilli, namely Lactobacillus fermentum ME-3 (DSM 14241) and Lactobacillus acidophilus 0.5×108 CFU /ml (group 4), daily for 15 days. Group 2 and 3 mice were challenged with a clinical isolate of S. Typhimurium (0.5×105 CFU/ml). The group 3 mice were additionally orally inoculated with lactobacilli for 5 days before and 10 days after the challenge with S. Typhimurium. Counts of salmonellae and lactobacilli in blood, intestine, liver and spleen were recorded; the morphological indices of inflammation in the same organs and oxidative stress-indicative biochemical status (lipid peroxidation, total antioxidative activity, redox ratio of glutathione and iron content) of gut mucosa were assessed on the 10th day after oral inoculation. The administration of probiotic lactobacilli of human origin did not increase the total count of lactobacilli in the terminal ileum of mice; however, hyperplasia of lymph nodes was registered in group 4 mice compared with group 1 mice. In the gut the lactobacilli that were antagonistic against S. Typhimurium in vitro neither decreased the count of salmonellae nor prevented the spread of the infection. In contrast, the antioxidative potential of L. fermentum ME-3 influenced gut mucosa by the reduction of iron level (pro-oxidant), lipid peroxidation and increased total antioxidative activity, glutathione redox value. We conclude that properties of probiotic lactobacilli assessed in vitro could be expressed differentially during in vivo study. The possibility to influence the pro- and antioxidant balance by specific probiotic lactobacilli with antioxidative properties in the course of inflammatory tissue damage could be further explored.