Isolation, identification, and probiotic properties of bacteriocin-producing Enterococcus faecium from yak

Abstract:

[Background] The abuse of antibiotics leads to the increase in drug resistance of common pathogenic bacteria in the intestinal tract of yaks. While probiotics have a promising application against drug-resistant bacteria.[Objective] To obtain yak probiotics with excellent probiotic properties is the purpose. [Methods] Twenty yak fecal samples were isolated and purified on MRS medium containing 0.5% CaCO₃, and strains with bacterial inhibitory activity were screened out by the Oxford cup method using Escherichia coli and Staphylococcus aureus as indicator bacteria. After acid and hydrogen peroxide were discharged, the bacteriocin-producing strains were screened out by acid and heat resistance test and protease sensitivity test, and identified by morphology and 16S rRNA sequence analysis. The probiotic properties were analyzed by in vitro bacteriostatic test against diarrhea pathogenic such as E. coli and Salmonella spp., measuring self-aggregation ability and hydrophobicity, tolerance to simulated gastrointestinal juice test, and antibiotic sensitivity test. [Results] Eleven strains of calcium soluble circles were isolated from 20 yak fecal samples, six of which had significant inhibitory effects on E. coli and S. aureus. Two strains of bacteriocin-producing lactic acid bacteria (SC6 and SC9) were obtained by re-screening, both of which were identified as Enterococcus faecium. The strain SC9 had obvious bacteriostatic effect on the bacteria of yak diarrhea, with good tolerance and intestinal adhesion ability in the simulated gastric and intestinal fluid, and it was sensitive to five commonly used antibiotics. [Conclusion] E. faecium SC9 has certain stress resistance and the potential as a probiotic.