Metabiotics or postbiotics are currently being considered as an alternative to cellular probiotics in the treatment of infectious and inflammatory diseases to maintain the mucosal immune system. The purpose of the work was to the study of the ability of Bifidobacterium bifidum 1 and Lactobacillus reuteri DSM 17938 cell-free extracts to influence innate immunity indices in vivo in a model of a generalized infection process in mice. Material and Methods. Cell-free extracts were obtained by culturing probiotics in their own disintegrates and contained their structural components and metabolites. Studies were performed using CBA mice of both sexes at the age of 2 months, weighing 19.0±2.0 g. The studied cell-free extracts were administered intraperitoneally at doses of 1000, 100 and 10 μg in 0.2 ml of sterile saline solution for three days. After the initiation of a lethal generalized infectious process by the intraperitoneal administration of 0.5 ml of Escherichia coli ATCC 25922 (3×108 CFU/ml), the clinical course of the disease was monitored and the number of dead animals was recorded for 10 days. Results and discussion. According to the literature data, the specified dose of Escherichia coli ensures the death of all animals within 36 hours, dosis certa letalis. In this study after the introduction of the indicated infectious dose, the percentage of dead animals within 36 hours was 90.9%. Preliminary administration of Bifidobacterium bifidum 1 and Lactobacillus reuteri DSM 17938 ensured the survival of more than 60% of the animals. After administration of Bifidobacterium bifidum 1, animal survival indices were 81.6% (1000 μg), 63.6% (100 μg), and 72.7% (10 μg). In the group of animals administered Lactobacillus reuteri DSM 17938, animal survival indices were 63.6% (1000 μg), 81.6% (100 μg), and 72.7% (10 μg). A sublethal generalized infectious process was caused by the intraperitoneal administration of 0.5 ml of Escherichia coli ATCC 25922 at a dose of 3×104 CFU/ml, which ensured the death of 30% of the animals. On the 2nd, 7th and 14th days blood was taken and the phagocytic activity of neutrophils was examined. The infectious process was characterized by a significant decrease in the phagocytic capacity of neutrophils. The use of Bifidobacterium bifidum 1 and Lactobacillus reuteri DSM 17938 led to a significant increase in the phagocytic index of neutrophils. The smallest decrease in the phagocytic neutrophil index on the 7th day was observed after administration of cell-free extracts at a dose of 100 μg per mouse. Phagocytic neutrophil indices on the 7th day of the infectious process were (61.55±2.0)% after administration of Bifidobacterium bifidum 1, (65.77±4.0)% after administration of Lactobacillus reuteri DSM 17938 and (45.18±2.0) without cell-free extracts applications. Conclusion. The results of the study indicated the ability of cell-free extracts to have a significant effect on the indices of innate immunity and open up prospects for their use as immunomodulators in the complex treatment of infectious diseases, as a means of non-specific prophylaxis of recurrence and reducing the risk of infection chronization.
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