奶牛子宫源海氏肠球菌的分离鉴定及安全性研究OA

This study aimed to isolate and screen excellent strains from the uterine of healthy,high-yield adult dairy cows,thus providing potential candidate strains for the development of microbial preparations against bacterial endometritis in dairy cows.The isolated and purified strains were identified via 16S rDNA sequencing.Systematic evaluations were conducted on the isolates regarding their growth characteristics,acid-producing capacity,adhesion ability,autoaggregation rate,surface hydrophobicity,and antibacterial activity.The safety of the strains was assessed through antibiotic susceptibility test,CCK-8 cytotoxicity assay,and in vivo safety test in mice.And a preliminary analysis was performed on the main antibacterial substances produced by the strains.The results demonstrated that two strains of Enterococcus hirae were successfully isolated in this study,which were designated as A8 and E5,respectively.Both strains exhibited favorable acid-producing and adhesion capabilities,which significantly inhibited the growth of Staphylococcus aureus and Escherichia coli.The main antibacterial substances produced by the two strains included hydrogen peroxide,bacteriocins,and organic acids.Additionally,both strains showed high sensitivity to nine commonly used antibiotics,including ciprofloxacin,tetracycline,erythromycin,rifampicin,ampicillin,chloramphenicol,and penicillin.They exerted no cytotoxic effects on bovine endometrial epithelial cells,and no uterine damage was observed in the mouse uterine perfusion test.In conclusion,Enterococcus hirae A8 and E5 possess excellent probiotic properties and biosafety,thus holding great potential for being developed as probiotic preparations in the clinical prevention and treatment of bovine endometritis.