牛源金黄色葡萄球菌单链抗体对奶牛乳腺炎的治疗效果评价

Evaluation of treatment effectiveness for bovine mastitis using the single-chain variable fragment against bovine Staphylococcus aureus

本文首先对患隐性乳腺炎的50头奶牛采取奶样,并对奶样进行了细菌分离鉴定及PCR检测,共检出金黄色葡萄球菌21株;随后对分离到的金黄色葡萄球菌进行了药敏试验,结果显示70%的金黄色葡萄球菌对青霉素产生了耐药性。为了研究针对金黄色葡萄球菌全菌抗原的单链抗体对奶牛乳腺炎的治疗效果,将表达单链抗体的重组质粒通过无针注射器注射到患病奶牛的乳腺（600μg/乳区）,48 h后再以相同的剂量注射一次。14 d后,奶样的加利福尼亚乳腺炎试验（California Mastitis Test,CMT）结果显示,治疗奶牛乳腺炎的有效率为83.33%,其中2例完全治愈。定期采集试验奶牛的乳样,并用PCR方法进行检测,发现第二次注射后的14 d内,奶样中未检测到重组质粒,说明重组质粒不能在奶牛体内长期残留。本研究为奶牛乳腺炎治疗抗体的研发提供了理论依据。

In order to investigate antimicrobial susceptibility of the main pathogens causing bovine mastitis,21 Staphylococcus aureus（ S.aureus） isolates from milk samples of 50 cows with subclinic mastitis were isolated,characterized and identified by PCR. The results showed that,in the 21 S. aureus strains,70% were resistant to penicillin. To evaluate the treatment effectiveness of the single-chain variable fragment（ sc Fv） against S. aureus,600μg of the recombinant plasmids（ pc DNA3. 1-sc Fvs）,which expressed the sc Fv,were prepared and injected aseptically into the mammary region of cows suffering from clinic and sub-clinic mastitis. 48 h later,the same experiment was conducted again. 14 days later,the California Mastitis Test（ CMT） was performed with the results that showed that the pc DNA3. 1-sc Fvs responded well to 83. 33% of the infected cows,two of which were cured. Further experiments were performed to find out whether the pc DNA3. 1-sc Fvs still existed in the milk of the cows injected with the recombinant plasmids from day 1 to day14. The PCR results showed no residue of the recombinant plasmids,implying a biosafety here. Our findings provided a scientific rationale for efficient control of bovine mastitis by applying sc Fv.