西北地区羊种布鲁氏菌遗传相关性分析

Genetic correlations among Brucella melitensis isolates from sheep in four provinces of northwest China

目的调查西北地区羊源布鲁氏菌的种型、分布及遗传相关性,揭示西北地区羊种布鲁氏菌种群和流行特征。方法用常规鉴定和AMOS-PCR对西北4省区的13个地区分离的布鲁氏菌进行种型鉴定,采用MLST和MLVA-16分型方法对菌株进行基因特征分析。结果常规鉴定和AMOS-PCR检测显示,本研究共分离羊种布鲁氏菌59株,其中22株来自内蒙古,17株来自新疆,13株来自甘肃,另有7株来自青海。羊种3型布鲁氏菌58株,羊种1型布鲁氏菌1株。MLST分析表明90%(53/59)的羊种布鲁氏菌为ST8序列型,为该地区主导流行种群。MLVA-11调查显示59株羊种布鲁氏菌聚为6个MLVA-11基因型,87%的菌株为MLVA-11基因116型,提示西北地区的流行菌株属于东地中海谱系。MLVA-16将59株羊种布鲁氏菌分为40个基因型,其中8个为共享基因型且每个基因型由2~7株来自相同地区的菌株构成,表明各共享基因型的病例由来自相同传染源引起的暴发流行。所有的共享MLVA-16基因型均由来自相同省区的菌株组成,提示各省区菌株呈现明显的地域聚集性特征。基于人群和羊脾分离菌株遗传比较显示,不同宿主来源的菌株组成多个完全相同的MLVA-16基因型,提示由羊到人的传播途径。结论羊种3型布鲁氏菌是西北地区动物布病的主要病原菌,疫羊是该区域人群布病的主要传染源。ST8克隆群是该地区的主导流行种群,各地区菌株MLVA基因型呈明显的地域聚集性特征。

Investigating the species/biovars,distribution patterns,and genetic correlations of Brucella from sheep in northwest China is critical to reveal the population and epidemiological characteristics of the Brucella melitensis.In this study,conventional identification and AMOS-PCR were used to determine the species/biovars of Brucella isolated from 13 regions in northwest China.MLST and MLVA-16 genotyping methods were used to analyze the genetic characteristics of the strains.Conventional identification and AMOS-PCR detection revealed that 59 Brucella melitensis were isolated in this study,including 22 strains from Inner Mongolia,17 strains from Xinjiang,13 strains from Gansu,and 7 strains from Qinghai,of which 58 strains were B.melitensis biovar 3,and one strain was B.melitensis biovar 1.MLST analysis indicated that 90%(53/59)of B.melitensis were of ST8 sequence type,the dominant epidemic population.The MLVA-11 survey demonstrated that 59 B.melitensis strains clustered into six MLVA-11 genotypes,and 87%of the strains were of MLVA-11 genotype 116.Therefore,the predominant strains in the northwest region were from the Eastern Mediterranean lineage.MLVA-16 divided 59 strains of B.melitensis into 40 genotypes,eight of which were shared genotypes.Each genotype was composed of two to seven strains from the same region,thereby indicating that the cases of each shared genotype were outbreaks from a common source of infection.All shared MLVA-16 genotypes comprised strains from the same province,thus indicating apparent regional clustering characteristics of strains in each province.In a genetic comparison between populations and isolated strains from the spleens of sheep,multiple identical MLVA-16 genotypes were found to be composed of strains from different hosts.These findings indicated a transmission pathway from sheep/goats to humans.B.melitensis biovar 3 was the main pathogen causing animal brucellosis in the northwest region,and infected sheep were the main brucellosis infection source in the regional population.The ST8 strains were the dominant epidemic population,and the MLVA genotype of strains in each region showed clear regional clustering characteristics.