Zaki M, Clark C G
Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom.
J Clin Microbiol. 2001 Mar;39(3):897-905. doi: 10.1128/JCM.39.3.897-905.2001.
An important gap in our understanding of the epidemiology of amebiasis is what determines the outcome of Entamoeba histolytica infections. To investigate the possible existence of invasive and noninvasive strains as one factor, the ability to differentiate individual isolates of E. histolytica is necessary. Two new loci containing internal repeats, locus 1-2 and locus 5-6, have been isolated. Each contains a single repeat block with two types of related direct repeats arranged in tandem. Southern blot analysis suggests that both loci are multicopy and may themselves be arranged in tandem arrays. Three other previously reported, internally repetitive loci containing at least two repeat blocks each with one or more related repeat units were also investigated. PCR was used to study polymorphism at each of these loci, which was detected to various degrees in each case. Variation was seen in the total number of bands obtained per isolate and their sizes. Nucleotide sequence comparison of loci 1-2 and 5-6 in five axenic isolates revealed differences in the number of repeat units, which correlated with the observed PCR product size variation, and in repeat sequence. Use of multiple loci collectively allowed differentiation of a majority of the 13 isolates studied, and we believe that these loci have the potential to be used as polymorphic molecular markers for investigating the epidemiology of E. histolytica and the potential existence of genetically distinct invasive and noninvasive strains.
我们在理解阿米巴病流行病学方面存在一个重要差距，即是什么决定了溶组织内阿米巴感染的结果。为了研究作为一个因素的侵袭性和非侵袭性菌株的可能存在，区分溶组织内阿米巴的各个分离株的能力是必要的。已分离出两个含有内部重复序列的新位点，即位点1-2和位点5-6。每个位点都包含一个单一的重复块，其中有两种相关的直接重复序列串联排列。Southern印迹分析表明，这两个位点都是多拷贝的，并且它们自身可能也排列成串联阵列。还研究了其他三个先前报道的内部重复位点，每个位点至少包含两个重复块，每个重复块都有一个或多个相关的重复单元。使用聚合酶链反应（PCR）来研究这些位点中每个位点的多态性，在每种情况下都不同程度地检测到了多态性。观察到每个分离株获得的条带总数及其大小存在差异。对五个无菌分离株中的位点1-2和位点5-6进行核苷酸序列比较，发现重复单元数量存在差异，这与观察到的PCR产物大小变化相关，并且在重复序列上也存在差异。共同使用多个位点能够区分所研究的13个分离株中的大多数，并且我们认为这些位点有潜力用作多态性分子标记，以研究溶组织内阿米巴的流行病学以及遗传上不同的侵袭性和非侵袭性菌株的潜在存在。
