MLVA typing of <i>Brucella melitensis</i> and <i>B. abortus</i> isolates of animal and human origin from India

Brucellosis is a widely prevalent zoonotic disease of major public health significance. A collection of <i>Brucella melitensis</i> and <i>Brucella abortus</i> field isolates of animal and human origin were subjected to MLVA-15 typing followed by phylogeography studies. The MLVA-15 analysis of <i>B. melitensis</i> (<i>n</i> = 65) field isolates resulted in 48 different profiles. The panel I marker bruce45 was found to be most conserved, while the rest of the panel I markers showed low to moderate length polymorphism. Among the panel II markers, bruce04, bruce16 and bruce30 showed a high discriminatory index. The MLVA-15 typing of 13 <i>B. abortus</i> field isolates revealed 13 different genotypes with panel II markers showing higher discriminatory ability vis-à-vis panel I. The minimum spanning tree analysis (MST) in comparison with isolates from the international database revealed that all <i>B. melitensis</i> and <i>B. abortus</i> isolates from this study belonged to the ‘Eastern Mediterranean’ and the ‘abortus C’ lineage, respectively. The MLVA-15 typing could differentiate field isolates of <i>B. abortus</i> and <i>B. melitensis</i> originating from different regions, reaffirming the technique’s potential of high resolution and suitability for local epidemiological studies. The MLVA scheme also has the advantage of comparison of local isolates with a worldwide database, allowing for phylogeographical studies.

布鲁氏菌病（Brucellosis）是一种广泛流行且具有重要公共卫生意义的人畜共患病。本研究收集了羊种布鲁氏菌（Brucella melitensis）与牛种布鲁氏菌（Brucella abortus）的动物来源及人类来源野外分离株，对其开展MLVA-15分型（多位点可变数目串联重复序列分析15型）及系统地理学研究。对n=65株羊种布鲁氏菌野外分离株的MLVA-15分析共得到48种不同的基因型谱，研究发现第一组标记（panel I）中的bruce45标记最为保守，其余第一组标记则呈现低至中等程度的长度多态性；在第二组标记（panel II）中，bruce04、bruce16及bruce30表现出较高的鉴别指数。对13株牛种布鲁氏菌野外分离株的MLVA-15分型结果显示，共获得13种不同的基因型，且第二组标记相较于第一组标记具有更高的鉴别能力。通过最小生成树（minimum spanning tree, MST）分析并与国际数据库中的分离株进行比对，结果显示本研究中的所有羊种布鲁氏菌与牛种布鲁氏菌分离株分别归属于“东地中海”进化分支与“abortus C”进化分支。MLVA-15分型技术可有效区分不同区域来源的羊种布鲁氏菌与牛种布鲁氏菌野外分离株，进一步证实了该技术具备高分辨率潜力，适用于本地流行病学研究；同时该MLVA分型方案还可实现本地分离株与全球数据库菌株的比对，为系统地理学研究提供支持。