对1例蓝氏贾第鞭毛虫感染者进行虫种分子鉴定并分析其感染来源。收集患儿与其父母、保姆的新鲜粪样，碘液染色后镜检，提取粪样DNA，采用巢式PCR扩增贾第虫磷酸丙糖异构酶（tpi）、谷氨酸脱氢酶（gdh）、β-贾第素（bg）基因并测序，通过BLAST、ChromasPro和MEGA 11.0等软件对基因序列进行系统进化分析并判断其集聚体类型。结果显示，镜下可见患儿粪样中有贾第虫滋养体和包囊。巢式PCR均扩增出约500 bp的条带，与贾第虫属tpi、gdh、bg基因片段一致，确认该患儿为贾第虫感染；患儿父母和保姆均无腹泻症状，但在其父亲粪样中发现贾第虫包囊，结合巢式PCR与测序结果分析，其父为贾第虫带虫者。基因比对分析结果显示，患儿父子二人粪样扩增出的tpi、gdh、bg基因序列一致性分别为99.8%、100%和98.5%，其中tpi基因序列与贾第虫集聚体AⅡ型（GenBank登录号：LC183963）的序列一致性分别为100%、99.8%，gdh基因序列与贾第虫集聚体AⅡ型（GenBank登录号：KF843931）的序列一致性分别为99.6%、100%，患儿bg基因序列与集聚体AⅢ型（GenBank登录号：LC183968）的序列一致性为99.2%，患儿父亲bg基因序列与集聚体AⅡ型（GenBank登录号：LC183975）的序列一致性为100%。系统进化树分析结果显示，患儿与其父亲所感染的贾第虫均与集聚体A型虫株聚在一支，且以tpi和gdh为靶基因进行亚型分析均与贾第虫集聚体AⅡ型聚在一支。由此判断患儿为贾第虫集聚体AⅡ型感染，且可能为家庭内部传播导致的家庭聚集性感染。

To investigate the molecular identification of Giardia lamblia isolated from an infected case and analyze the source of infection. Fresh fecal samples of the patient and his parents and the nanny were collected for iodine solution staining and microscopic examination. Fecal DNA was extracted, and nested PCR was used to amplify the triosephosphate isomerase (tpi), glutamate dehydrogenase (gdh) and beta-giardin (bg) gene for sequencing. The homology comparison and phylogenetic analysis of gene sequences were performed by BLAST, ChromasPro and MEGA 11.0 software to determine the assemblages. The results showed that there were trophozoites and cysts in the fecal of the patient through microscopic examination. Nested PCR amplified bands of about 500 bp, which were consistent with the tpi, gdh and bg gene fragments of G. lamblia, confirming the infection of G. lamblia. None of the patient’s parents and nanny had diarrhea symptoms, but G. lamblia cysts were found in the stool specimen of his father. Combined with nested PCR and sequencing results, the father was a G. lamblia carrier. The results of the gene comparison showed that the percent identity of tpi, gdh and bg genes sequence amplified from fecal samples of the patient and his father was 99.8%, 100% and 98.5%, respectively. The percent identity of tpi gene sequence amplified from the fecal samples of the patient and his father showed 100% and 99.8% with G. lamblia assemblages AⅡ (GenBank accession no. LC183963), respectively. The amplified gdh gene sequence showed 99.6% and 100% with assemblages AⅡ (GenBank accession no. KF843931), respectively. The percent identity between the bg gene sequence amplified from the patient fecal sample and the sequence of assemblages AⅢ (GenBank accession no. LC183968) is 99.2%, while the percent identity between the bg gene sequence amplified from the father’s fecal sample and the sequence of assemblages AⅡ (GenBank accession no. LC183975) is 100%. The results of phylogenetic tree analysis showed that both the patient and his father were infected with G. lamblia and clustered in the same cluster as assemblages A, and sub-genotype analysis using tpi and gdh as target genes were conducted, which clustered in the same cluster as assemblages AⅡ. Therefore, it can be determined that the patient was infected with G. lamblia assemblages AⅡ, and it could be a family cluster infection caused by internal transmission within the family.