Dysbiotic shifts in intestinal and pharyngeal microflora were studied in 22 normal volunteers in 9-, 14-, 105- and 520-d chamber experiments simulating some of the spaceflight factors. Two preparations were administered to prevent pharyngeal and intestinal dysbiosis: oral dry probiotic based on indigenous intestinal Enterococci and topical collagen-immobilized Lactobacterin based on indigenous intestinal Lactobacilli. Topical autopmrobiotic lactobacterin reduced the growth of opportunistic pathogens in the throat during the experiments. Oral autoprobiotic based on Enterococci reduced the content of intestinal opportunistic pathogens, supporting the high level of protecting microflora. Most of autostrains are free from pathogenicity factors, nevertheless, implementation of genetic testing of indigenous strains are reasonable.