Molecular characterizations of the microsporidian pathogen Enterocytozoon bieneusi at the ribosomal internal transcribed spacer (ITS) locus have identified nearly 500 genotypes in 11 phylogenetic groups with different host ranges. Among those, one unique group of genotypes, Group 11, is commonly found in dogs. Genetic characterizations of those and many divergent E. bieneusi genotypes at other genetic loci are thus far impossible. In this study, we sequenced 151 E. bieneusi isolates from several ITS genotype groups at the 16S rRNA locus and two new semi-conservative genetic markers (casein kinase 1 (ck1) and spore wall protein 1 (swp1)). Comparison of the near full (~1,200 bp) 16S rRNA sequences showed mostly two to three nucleotide substitutions between Group 1 and Group 2 genotypes, while Group 11 isolates differed from those by 26 (2.2%) nucleotides. Sequence analyses of the ck1 and swp1 loci confirmed the genetic uniqueness of Group 11 genotypes, which produced sequences very divergent from other groups. In contrast, genotypes in Groups 1 and 2 produced similar nucleotide sequences at these genetic loci, and there was discordant placement of ITS genotypes among loci in phylogenetic analyses of sequences. These results suggest that the canine-adapted Group 11 genotypes are genetically divergent from other genotype groups of E. bieneusi, possibly representing a different Enterocytozoon sp. They also indicate that there is no clear genetic differentiation of ITS Groups 1 and 2 at other genetic loci, supporting the conclusion on the lack of strict host specificity in both groups. Data and genetic markers from the study should facilitate population genetic characterizations of E. bieneusi isolates and improve our understanding of the zoonotic potential of E. bieneusi in domestic animals.

微孢子虫病原体Enterocytozoon bieneusi在核糖体内部转录间隔区 (ITS) 位点的分子特征已在 11 个不同宿主范围的系统发育组中鉴定出近 500 种基因型。其中，一组独特的基因型，第 11 组，常见于狗。迄今为止，在其他基因座上对那些和许多不同的E. bieneusi基因型进行遗传表征是不可能的。在这项研究中，我们测序151 E. bieneusi从在的16S rRNA基因座几个ITS基因型组和两个新的半保守的遗传标记（酪蛋白激酶1（分离物CK1）和孢子壁蛋白1（SWP1))。比较近乎完整（~1,200 bp）的 16S rRNA 序列显示，第 1 组和第 2 组基因型之间主要有 2 到 3 个核苷酸取代，而第 11 组分离株与那些分离株的差异有 26 个（2.2%）核苷酸。ck1和swp1基因座的序列分析证实了第 11 组基因型的遗传独特性，其产生的序列与其他组非常不同。相比之下，第 1 组和第 2 组中的基因型在这些基因座上产生了相似的核苷酸序列，并且在序列的系统发育分析中，ITS 基因型在基因座之间的位置不一致。这些结果表明犬适应的第 11 组基因型与E. bieneusi 的其他基因型组在遗传上不同，可能代表不同的Enterocytozoon sp. 他们还表明 ITS 第 1 组和第 2 组在其他基因座上没有明显的遗传分化，支持了两组都缺乏严格宿主特异性的结论。研究中的数据和遗传标记应有助于对E. bieneusi分离株进行种群遗传表征，并提高我们对家畜中E. bieneusi人畜共患病潜力的理解。