MLVA方法对奶牛乳房炎金黄色葡萄球菌的分型研究及效果评价

Multiple-locus Variable-number Tandem Repeat Analysis of Polymorphism and Genetic Relationships of S.aureus Isolated from Bovine Mastitis

奶牛乳房炎金黄色葡萄球菌的分型对预防菌株在牛体之间传播、了解菌株地域性分布特点及针对性疫苗的研制均有重要的意义。本研究旨在将多位点可变数目串联重复序列分析(MLVA)法应用于国内乳房炎金葡菌的分型研究,以进行分子流行病学调查。同时,将其与16-23SrRNA基因间区分析法(RS-PCR)的分型结果比较,以评价MLVA法对乳房炎金葡菌的分型效果。作者建立MLVA方法(多重PCR体系)对27株乳房炎金葡菌进行分型,同时应用RS-PCR法进行分型。结果2种方法均可将8个地区17个牛场分离到的27株菌全部分型,分型率为100%。MLVA法将菌株分为19个型,不同牛场来源的金葡菌均属于不同型,相同牛场来源的菌株除上海和北京某牛场外均属于相同型;此方法的分型力为0.969。RS-PCR法将菌株分为10个型,其中Ⅰ、Ⅱ和Ⅴ型菌株均来源于不同地区,分型力为0.829。结果显示,MLVA分型法具有快速、操作方便和分型能力强等特点,可应用于乳房炎金葡菌的分子流行病学研究。同时,研究表明,我国不同牛场的乳房炎金葡菌具有型特异性,该结果与少数优势型金黄色葡萄球菌引起绝大多数乳房炎的报道相反。

Molecular typing of Staphylococcus aureus is valuable for presenting the strain spreading,detecting the strain geographical distribution and developing specific vaccine.We aimed at developing a MLVA method to type S.aureus isolates coming from Chinese herds,and then to perform a molecular epidemiological study.Another aim is to evaluate the discriminatory power of MLVA method by comparing with RS-PCR typing method.MLVA method（multiplex PCR system） was constructed to type 27 S.aureus isolated from different regions and herds.Meanwhile,all of the isolates were typed using RS-PCR method.Both of the methods can type all 27 isolates obtained from 17 herds located in eight regions.Nineteen distinct types were identified by MLVA method,all of which belong to individual herds.And the strains with the same source were typed identical other than those from two herds in Shanghai and Beijing.The discriminatory power of MLVA is 0.969.As for RS-PCR method,it can identify the isolates into 10 types,of which type Ⅰ,Ⅱ and Ⅴ were distributed in different regions.The discriminatory power of RS-PCR is 0.829.From the above results,we conclude that MLVA is a rapid and convenient method which shows good discriminatory power to type bovine S.aureus isolates.Meanwhile we infer that types of S.aureus are more likely to be restricted to a single herd,than found in multiple herds in China.