Identification of zoonotic isolates of Blastocystis by using polymorphic genomic DNA

由于从多种动物中广泛分离到了芽囊原虫，人和动物中分离到的芽囊原虫在遗传和核型上存在着广泛的异质性，因此很难阐明从动物中分离出的生物与人芽囊原虫是相同还是不同。因此，在这项研究中，我们从已知的人芽孢杆菌菌株的随机扩增多态性DNA分析中开发了几个序列标记位点(STS)引物。由于STS引物只能扩增出与小亚基核糖体DNA序列相对应的不同亚型，因此STS引物可以作为芽囊原虫种群间基因分型的工具。用STS引物对哺乳动物和鸟类的不同分离株进行扩增时，大多数分离株扩增出不同的引物，提示动物分离株属于人畜共患病的基因类型。这些结果表明，从动物体内分离的芽囊原虫是人类潜在的感染源。

Since Blastocystis organisms have been widely isolated from a variety animals and extensive genetic and karyotypic heterogeneity have been demonstrated among Blastocystis isolates from humans and animals, it is difficult to clarify whether isolated organisms from animals are identical to or different from human B.hominis. In this study, therefore, we developed several sequenced-tagged site (STS) primers from random amplified polymorphic DNA analysis of known strains of B.hominis. Since the STS primers only amplified the distinct subtypes which correspond to the phylogenetically different clades inferred from the small subunit ribosomal DNA sequences, the STS primers can be used as a tool to type genotypes among polymorphic Blastocystis populations. When various isolates from mammals and birds have examined with PCR amplification by using the STS primers, most of the isolates were amplified with distinct primer, suggesting a zoonotic genotypes of animal isolates. These results indicated that Blastocystis organisms isolated from animals are potential sources of human infections.