为明确1例腹泻患者感染的蓝氏贾第鞭毛虫（简称“贾第虫”）的感染来源和遗传特征，收集该患者的新鲜粪样，综合采用镜检、实时荧光定量PCR和巢式PCR方法进行病原检测，对小亚基核糖体RNA（SSU rRNA）、磷酸丙糖异构酶（tpi）、谷氨酸脱氢酶（gdh）、β-贾第素（bg）和翻译延伸因子1α（ef1α）进行宏基因组测序并分析，通过序列比对及系统进化树构建分析，开展多位点基因分型与遗传进化研究。镜检与实时荧光定量PCR均确认贾第虫感染。巢式PCR中仅gdh和ef1α基因扩增成功，宏基因组测序成功检测到SSU rRNA基因序列。多位点基因分型显示，本研究获得的分离株DXH001为集聚体B型，未发现混合感染。系统发育分析表明，DXH001分离株的gdh基因与比利时人源株EU847734的序列一致性达100%，属BⅣ亚型；ef1α基因与澳大利亚人源分离株HQ179598的序列一致性达98.43%，SSU rRNA基因与美国人源株U09491的序列一致性达90.45%，均聚类于B型分支。SSU rRNA基因与人源参考序列U09491相比存在35个碱基替换和5个缺失，其序列差异可能主要与样本中目标序列丰度较低，导致测序数据量不足有关；gdh与ef1α基因的变异较为保守，未引起重要功能改变。本研究通过多位点基因分析鉴定DXH001株为蓝氏贾第鞭毛虫集聚体BⅣ亚型，提示该亚型存在跨地域传播风险。宏基因组测序在低丰度靶标检测中展现出较高灵敏度，可作为常规分子分型的有效补充。

To clarify the infection source and genetic characteristics of Giardia lamblia isolated from a diarrheal patient, fresh fecal sample of the patient was collected. Microscopy, real-time fluorescent quantitative PCR and nested PCR were comprehensively applied for pathogen detection. Metagenomic sequencing and analysis were performed targeting the small subunit ribosomal RNA (SSU rRNA), triosephosphate isomerase (tpi), glutamate dehydrogenase (gdh), β-giardin (bg) and translation elongation factor 1α (ef1α). Multilocus genotyping and genetic evolution analysis were carried out via sequence alignment and phylogenetic tree construction. Both microscopy and real-time fluorescent quantitative PCR confirmed Giardia infection. Only the gdh and ef1α genes were successfully amplified by nested PCR, and the SSU rRNA gene sequence was successfully detected by metagenomic sequencing. Multilocus genotyping showed that the isolate DXH001 obtained in this study belonged to assemblage B, and no mixed infection was detected. Phylogenetic analysis indicated that the gdh gene of isolate DXH001 shared 100% sequence identity with the human-derived strain EU847734 from Belgium, belonging to subtype BⅣ; the ef1α gene shared 98.43% sequence identity with the human-derived isolate HQ179598 from Australia, and the SSU rRNA gene shared 90.45% sequence identity with the human-derived strain U09491 from the United States, both clustered into the assemblage B branch. Compared with the human-derived reference sequence U09491, the SSU rRNA gene had 35 base substitutions and 5 deletions, and the sequence difference was mainly related to the insufficient sequencing data volume caused by the low abundance of the target sequence in the sample; the variations of gdh and ef1α genes were relatively conservative, which did not cause significant functional changes. In this study, the isolate DXH001 was identified as G. lamblia assemblage BⅣ via multilocus genetic analysis, suggesting the trans-regional transmission risk of this subtype. Metagenomic sequencing shows high sensitivity in low-abundance target detection, which can serve as an effective supplement for conventional molecular genotyping.