Effects of plant extracts on the growth of beneficial indigenous lactic acid bacteria (BLAB) for their potential use in preventing bovine reproductive tract infections

Abstract

There is a renewed interest in products based on phytocompounds, prebiotics and probiotics in recent years, applied to different hosts to exert a wide variety of effects. The microbiome of the bovine reproductive tract can become unbalanced for many reasons, favoring the entry and proliferation of pathogenic microorganisms, currently treated with antibiotics that exert adverse effects and generate antimicrobial resistance. To deal with this situation, "phytobiotic" formulas are proposed that combine phytocompounds and probiotics. This study aims to determine the compatibility of beneficial autochthonous lactic acid bacteria (BALB) with plant extracts, prebiotics and vitamins, to incorporate them into intravaginal formulas with therapeutic activity. Nine beneficial strains isolated from different bovine ecosystems were evaluated against nine phytocompounds, two prebiotics and five vitamins. Compatibility was assayed using the diffusion technique on agar plates, and the effect of the phytocompounds on the growth of lactic acid bacteria by microplates. The growth of all the strains was affected by some plant extracts, showing a stimulating or inhibitory effect. By the qualitative method, only vitamin A affected the viability of Lactobacillus johnsonii CRL1702 at concentrations higher than 7.5 mg/ml, however, when studying the growth kinetics of the strains with the phytocompounds, the results show that the effect was different in each of one the associated strains + plant extracts, indicating a strain specific effect of plant extacts on each BALB strain. Lapacho and Malva have a stimulating effect on most of the microorganisms, while Garlic and Belladonna inhibited the growth of all of them. Plant extracts at different concentrations did not inhibit the growth of most of the pathogens responsible for endometritis. On the other hand, the highest concentrations of phenolic compounds were detected in Echinacea, Lapacho and Llantén; and the best percentages of antioxidant activity were evidenced in Garlic, Blueberry and Chamomile (<60%). The results obtained in this stage are original, since the combination of natural extracts with lactobacillus strains for veterinary application was not studied previously.