Changes in the microflora of man during long-term confinement.

Extended space missions may change the human normal microflora, including the intestinal flora. The bacterial composition of the intestinal microflora is an important factor in natural resistance to infection. During the year-long medico-engineering experiment human intestinal microflora was thoroughly studied. It was necessary to collect more detailed information concerning the composition in healthy people. 83 microbiological tests of faeces of 27 healthy male subjects were carried out. It was found that spore-less anaerobic bacteria predominated in the fecal microflora, reaching 90% of total micro-organisms. Aerobic micro-organisms were less than 6% of total micro-organisms. Long-term enclosure of men was shown to induce changes in the intestinal microflora which involved a sharp reduction of different microbial groups, and occasionally complete elimination of certain representatives of the intestinal flora. The composition tended to be simplified. A study of the isolated cultures of Cl. perfringens demonstrated an increased amount of strains with toxicogenic properties. Staphylococci were isolated from the test subjects during their long-term enclosure. The pharynx and nose of the three test subjects were examined and 1445 staphylococcal strains were isolated, of which 745 strains (51.5%) were coagulase producers. In 745 strains phage-type, coagulase, toxicity, hemolysins, lecitinase, fibrinolysin and DNA-ase were determined. Phage-typing of the isolated staphylococci revealed a microbial exchange between the men. Staphylococcal strains of the same phage-type (29/52) isolated during the experiment showed an increase of the toxin titre (from 1:40-1:80 to 1:640-1:1280) and development of additional pathogenic properties that were not found previously. An increase in beta-hemolysin and fibrinolysin production and an acceleration of DNA-ase activity. Experiments on mice demonstrated increased virulence of the staphylococcal strains isolated by the end of the experiment. The data are discussed from the point of view of the immunological responses of the human body.