[Comparative evaluation of the antagonistic activity of collection lactobacilli against the multidrug-resistant Klebsiella pneumoniae]

Taking into account the known data on the high prevalence of multi-drug-resistant Enterobacteriaceae, such as Klebsiella spp., enterohemorrhagic Escherichia coli, and their properties to maintain viability in fermented milk products when using technologies in which, along with starter microorganisms, some enterobacteria with increased resistance to environmental factors (primarily active acidity) can survive and even multiply, the search for new strains of lactic acid probiotic bacteria with a pronounced antimicrobial effect are currently one of the most relevant areas of research in food biotechnology. Representatives of the Lactobacillus genus are currently considered as the most promising objects for the search for producers with probiotic properties. Their antagonistic activity is an important condition for ensuring the biological safety of foods created using fermentation and for developing effective measures to combat conditionally pathogenic and pathogenic microorganisms of the highest priority in terms of epidemiological significance. The aim of the research was to study the antagonistic activity of collectible probiotic Lactobacillus strains in relation to multi-resistant Klebsiella pneumoniae, to assess their suitability in the production of specialized fermented milk products. Material and methods. To determine the antagonistic activity of Lactobacillus collection strains in relation to the Klebsiella pneumoniae strain, two methods were used: co-cultivation and diffusion into agar using wells. Results. As a result of the study of 2 strains of lactic acid bacteria - Lactobacillus helveticus NK1 and Lactobacillus (Lacticaseibacillus rhamnosus) rhamnosus F as antagonists against Klebsiella pneimopiae hospital strain, characterized by multiresistance to antibiotics of different groups, the high efficacy of the L. rhamnosus F. strain was confirmed. Antagonistic activity of the L. helveticus NK1 strain was insignificant, which suggests the variability of Klebsiella and the importance of searching for an antagonist strain with the widest possible spectrum of action. Conclusion. The confirmed high antagonistic activity of the L. rhamnosus F strain makes it possible to recommend it for inclusion in starter cultures. The prospects of using the L. rhamnosus F strain, including for the production of fermented milk products for therapeutic nutrition and other special dietary uses, and for use in the diets of people with dysbiotic disorders, patients with intestinal infections, in particular, caused by multi-resistant strains of Klebsiella pneumoniaе, related to nosocomial infections, are shown. However, further research is needed to determine (identify) the mechanisms of the antimicrobial action of L. rhamnosus F. strain.

[Development of biotechnology of fermented milk product with Lactobacillus reuteri LR1 and the evaluation of its functional property in experiment in vitro and in vivo]

In this article the biotechnology of the dairy product based on the probiotic strain of Lactobacillus reuteri LR1 is presented. The following conditions of milk fermentation were screened: fermentation by monoculture of Lactobacillus reuteri LR1, fermentation by monoculture of Lactobacillus reuteri LR1 with addition of yeast extract as growth-promoting factor, and combined fermentation by Lactobacillus reuteri LR1, Lactobacillus helveticus NK1 and Streptococcus thermophilus (HTC). It had been demonstrated that after 8 hours of cultivation the number of Lactobacillus reuteri LR1 cells in the monoculture with introduced yeast extract was up to 5,9×10⁸ CFU/cm³ whereas cell count for the monoculture without yeast extract introduction was 1,6×10⁷ CFU/cm³. The optimized biotechnological parameters of the dairy product fermentation, which provided the required Lactobacillus reuteri LR1 cell count, were as follows: Lactobacillus reuteri LR1 starter dosage of 6%, HTC starter dosage of 3-4%, fermentation temperature of 37±1 °C, and fermentation duration of 6 hours. The developed product possessed an apparent antagonistic activity against test-cultures of such pathogenic and opportunistic microorganisms as E. coli ATCC 25922, Salmonella typhimurium, Staphylococcus aureus ATCC 6538 and Klebsiella pneumoniae. The survival of the test-cultures cultivated with the obtained dairy product on the first cultivation day was from 36 to 46% and on the second - from 8 to 20%, in comparison with the pure test-cultures. The investigation of the functional properties of the obtained dairy product was carried out by the single-factor experiment with the albino Wistar rat-stock (initial body weight 160±10 g, n=10 in each group). Its positive effect on the rats' microbiome composition and lipid exchange indices has been demonstrated. It had been shown that the administration of the obtained dairy product in the rats' diet (5 ml per day per os) during 30 days didn't cause any abnormalities in the health status and behavior of the laboratory animals of spf-category. The number and distribution of leucocytes and lymphocytes, and granulocytes in all rats' populations (intact, control and treatment) were within the normal range. Upon the introduction of the developed dairy product into the rats' diet, the increased levels of bifidobacteria, lactic acid bacteria and typical for normal rats' microflora enterobacteria were observed in the rats' microbiome. As for the biochemical indices that characterize rats' lipid metabolism, the rats consuming fermented dairy products (control and treatment) demonstrated statistically significant reduction of blood serum cholesterol level compared to the intact rat group; additionally the rats consuming the developed in this study dairy product (treatment) demonstrated statistically significant reduction of blood serum triglyceride level compared to the intact rats. Utilized in this study Lactobacillus reuteri LR1 is the first strain that was purified in Russia and characterized as useful for manufacturing of the probiotic food products, since currently only Lactobacillus reuteri strains of foreign origin can be seen on the market.