Departamento de Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, México DF, Mexico.
Infect Genet Evol. 2013 Jul;17:243-52. doi: 10.1016/j.meegid.2013.04.021. Epub 2013 Apr 25.
Although Entamoeba histolytica is one of the most prevalent intestinal parasites, how the different strains of this species are distributed all over the world and how different genotypes are associated with the infection outcome are yet to be fully understood. Recently, the use of a number of molecular markers has made the characterization of several genotypes in those regions with high incidence of amoebiasis possible. This work proposes the first genealogy of E. histolytica, with an haplotype network based on two tRNA gene-linked array of Short Tandem Repeats (STRs) reported until today, and 47 sequences from 39 new isolates of Mexican Amoebic Liver Abscesses (ALA) samples. One hundred and three sequences were obtained from D-A locus, their information about the geographic region of isolation as well as clinical diagnosis were also collected. One hundred and five sequences from N-K2 locus were also obtained as well as the region of isolation, but the information about clinical diagnosis was not available in all cases. The most abundant and widely distributed haplotype in the world is the one of E. histolytica HM1:IMSS strain. This was found in Mexico, Bangladesh, Japan, China and USA and is associated to symptomatic patients as well as asymptomatic cyst passers. Many other haplotypes were found only in a single country. Both genealogies suggest that there are no lineages within the networks that may be related to a particular geographic region or infection outcome. A concatenated analysis of the two molecular markers revealed 12 different combinations, which suggests the possibility of genetic recombination events. The present study is the first to propose a global genealogy of this species and suggests that there are still many genotypes to be discovered. The genotyping of new isolates will help to understand the great diversity and genetic structure of this parasite.
虽然溶组织内阿米巴是最常见的肠道寄生虫之一，但这种物种的不同菌株如何分布在世界各地，以及不同的基因型如何与感染结果相关，仍有待充分了解。最近，许多分子标记的使用使得在那些阿米巴病高发地区对几种基因型进行特征描述成为可能。这项工作提出了溶组织内阿米巴的第一个系统发育树，该系统发育树基于迄今为止报道的两个 tRNA 基因连接的短串联重复（STR）阵列构建的单倍型网络，以及来自 39 个新分离的墨西哥阿米巴性肝脓肿（ALA）样本的 47 个序列。从 D-A 基因座获得了 103 个序列，还收集了它们关于分离的地理区域和临床诊断的信息。还获得了 105 个来自 N-K2 基因座的序列以及分离的区域，但并非所有情况下都有关于临床诊断的信息。在世界上最丰富和分布最广的单倍型是溶组织内阿米巴 HM1:IMSS 株。在墨西哥、孟加拉国、日本、中国和美国都发现了这种单倍型，它与有症状的患者以及无症状的包囊携带者都有关联。许多其他单倍型仅在一个国家发现。两个系统发育树都表明，网络中没有与特定地理区域或感染结果相关的谱系。对这两个分子标记的串联分析显示了 12 种不同的组合，这表明可能存在遗传重组事件。本研究首次提出了该物种的全球系统发育树，并表明仍有许多基因型有待发现。对新分离株的基因分型将有助于了解这种寄生虫的巨大多样性和遗传结构。
