芽囊原虫的分离鉴定及致病性分析

Isolation,identification,and pathogenicity of Blastocystis sp

摘要:

芽囊原虫(Blastocystis sp.)是一种在全球范围内广泛分布的人畜共患单细胞真核生物，主要寄生于宿主肠道。该寄生虫具有丰富的遗传多样性，目前已报道42种有效亚型(ST1−ST17，ST21，ST23−ST46)，其中ST1型、ST2型和ST3型流行最为广泛，但芽囊原虫的致病能力及不同亚型之间的致病性差异一直存在争议。【目的】评价ST1型、ST2型和ST3型芽囊原虫的致病能力，同时探讨3个亚型芽囊原虫之间是否存在致病性差异。【方法】从人和猕猴新鲜粪便中分离芽囊原虫，通过形态学观察，18S rRNA基因扩增、测序和聚类分析进行芽囊原虫鉴定。将获得的ST1型、ST2型和ST3型芽囊原虫感染BALB/c小鼠，探究芽囊原虫在小鼠体内的分布特点，并根据芽囊原虫感染后小鼠状态、体重变化、饲转率及死亡率，比较3种亚型虫株对小鼠的致病能力，通过病理学观察比较不同亚型芽囊原虫对小鼠肠道组织损伤能力。【结果】本研究成功分离鉴定出ST1型、ST2型和ST3型3种亚型芽囊原虫。芽囊原虫感染小鼠后主要分布在小鼠肠道，对小鼠的健康状况产生影响，ST3亚型芽囊原虫的大量感染会导致小鼠死亡，但ST1型、ST2型和低剂量的ST3型芽囊原虫不影响小鼠的生活。病理学观察结果显示芽囊原虫感染损伤小鼠肠道组织。【结论】芽囊原虫通过损伤肠道组织对宿主造成危害，但不同亚型之间存在致病性差异，ST3亚型芽囊原虫具有较强的致病性，本研究为进一步研究芽囊原虫致病机理奠定基础，也为其公共卫生意义的评估提供参考数据。

Abstract:

Blastocystis sp.is a widespread unicellular protozoan mainly parasitizing the intestines of humans and animals.This parasite has rich genetic diversity,with 42 subtypes (ST1–ST17,ST21,ST23–ST46) reported,of which ST1,ST2,and ST3 are prevalent.However,the pathogenicity levels and the pathogenicity differences among different subtypes have been controversial.[Objective] To determine the pathogenicity of ST1,ST2,and ST3 and explore whether there are differences in the pathogenicity between the three subtypes of Blastocystis sp.[Methods] Blastocystis sp.strains were isolated from fresh human and macaque faeces and identified by morphological observation,18S rRNA gene amplification and sequencing,and cluster analysis.After BALB/c mice were infected with strains of ST1,ST2,and ST3,the distribution characteristics of the parasites in vivo were observed.In addition,the clinical signs,weight gain,feed conversion rate,and mortality of the infected mice were recorded to compare the pathogenicity of the three subtypes.Finally,the pathological changes in the intestines of mice were observed.[Results] Three subtypes of Blastocystis sp.,ST1,ST2 and ST3,were successfully isolated and identified.Animal challenge results showed that the parasites predominantly colonized the intestine and negatively affected the health of mice.A high dose of ST3 resulted in death in mice,while ST1,ST2,and low doses of ST3 did not affect the survival of mice.Blastocystis sp.damaged the intestinal tissue of challenged mice.[Conclusion]Blastocystis sp.causes harm to the host by damaging the intestine.The pathogenicity varies among different subtypes and ST3 has stronger pathogenicity.This study lays a foundation for further studying the pathogenicity mechanism and provides data for assessing the threat ofBlastocystis sp.to public health.