The intestinal microbiota of rats under the influence of biotechnological strains of microorganisms from various taxonomic groups

Abstract

Introduction. The microbiota of the gastrointestinal tract (GIT) plays an essential role in maintaining human health. Many factors, including industrial pollutions with biotechnological strains of microbes, can affect the normal balance of intestinal microbiota. The biotechnological industry nowadays produces a wide range of products for medical and veterinary use, agriculture, food, chemical industries, etc. To develop hygienic standards that regulate the possible adverse effect of biotechnological strains of microorganisms on workers’ health, the intestinal microflora of rats in the experiment can be studied. The data obtained were used as the basic concept in elaborating state sanitary standards for limitations of the concentrations of biotechnological strains of microorganisms in the ambient air of the working area and settlements’ atmosphere. Materials and methods. We have tested 52 strains of microorganisms applied in biotechnology as producers of a variety of biological substances. They included members of different taxonomic groups: gram-positive and gram-negative bacteria, actinomycetes, molds, and yeasts. The experiments were carried out on conventional male and female white rats (290-320 g, body weight). Each test and control group of animals included eight animals. The strains of microorganisms mentioned above were given to animals by inhalation of minimal effective doses of microbes in the concentrations of 103-108 CFU/m3 during one month. To demonstrate possible adverse effects to gut microflora, the routine bacteriological examination of animal feces was performed. To do this, after the priming, the 10-fold dilutions of animal feces in sterile saline were inoculated onto a set of general-purpose and selective culture media for Enterobacteriaceae members, staphylococci, enterococci, clostridia, bifidobacteria, lactobacilli, and fungi, with subsequent identification of the genus of the isolated microorganism. After that, the concentrations of microorganisms were calculated and measured in lg of CFU/g of feces. The Institutional Ethical Committee of Animal Care and Use of the Pirogov Russian National Research Medical University approved all procedures involving animals. The results of experiments were analyzed with a simple t-test using Statistica (v.6.0, Stat Soft, USA) and Microsoft Office Excel 2007. Results were considered statistically significant when p < 0.05. Results. The most notable changes in the composition of the intestinal microbiota were observed after inhaling of yeasts of genus Candida at the level of 103-104 CFU/m3 and in cases of exposure to molds (Aspergillus awamori, Penicillium funiculosum, and Tolypocladium cylindrosporum) in the concentration of 2•104 CFU/m3, and gram-negative bacteria of the genus Alcaligenes and genus Pseudomonas at 5•105 CFU/m3. We observed a dramatic decrease of Escherichia coli and the increase of gram-positive bacteria (staphylococci, enterococci). For some genera of biotechnological strains, a significant decline in the content of lactobacilli was also shown. On the other hand, Rhodococcus did not cause any disturbances even at high concentrations in the ambient air. Conclusion. The obtained data can be used to develop biosafety and hygienic standards for industrial microbes to help decrease or minimize the occupational risk of infection or undesirable allergic effect when working with biotechnological strains of microbes in the ambient air of residential areas.