Probiotic properties of lactic acid bacteria isolated from the reproductive system of cows on eco-farms in the North-West of Russia

Background. The application of probiotics capable of restoring the normal microbiota of the cow’s reproductive tract and enhancing resistance to infections represents a promising direction. Purpose.The aim of this study was to isolate, identify, and characterize promising lactic acid bacteria strains from the reproductive tract of healthy cows for the development of a novel biopreparation aimed at the prevention of endometritis. Materials and methods. Biological material (vaginal wall swabs) for the isolation of prospective Lactobacilli strains was collected from ten clinically healthy dairy cows on three eco-farms (located in the North-Western region of the Russian Federation and the Republic of Karelia). Isolation of pure cultures was performed by plating serial dilutions onto a selective agar medium. Identification was carried out using standard microbiological methods, including PCR analysis. Antagonistic activity against ten pathogenic and opportunistic microorganisms was assessed in vitro using the agar diffusion method. Results. A total of 95 Lactobacilli isolates were obtained. Screening of 42 lactobacilli strains revealed 19 active and moderately active variants exhibiting antimicrobial activity against pathogens. Strain E-49 (Lactobacillussp.) demonstrated the highest antagonistic activity againstClostridium perfringens(38 ± 1,0 mm) andEnterococcus faecalis(32 ± 1,9 mm). Strain E-52 (Lactobacillussp.) actively inhibited the growth ofPenicilliumsp. (37 ± 1,5 mm) andStreptococcus agalactiae(21 ± 0,9 mm). None of the tested strains exhibited hemolytic activity. Several active strains, such as E-49, E-52, and E-10, demonstrated stable titers of viable cells over 30 days of storage (2,4×109± 1,5×108and 1,4×109± 7,0×107CFU/mL for E-52 at 10 and 30 days, and 7,3×109± 6,2×108CFU/mL for E-10 at 30 days) and optimal pH values (3,8-4,2).