CHINESE JOURNAL OF PARASITOLOGY AND PARASITIC DISEASES ›› 2023, Vol. 41 ›› Issue (3): 380-383.doi: 10.12140/j.issn.1000-7423.2023.03.018

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Molecular identification and genetic tracing of Giardia lamblia isolated from an infected case

WANG Dan1,2(), HE Zhiquan1,2, LIU Ying1,2, LIU Lingzhi3, CHEN Huihui4, JIANG Tiantian1,2, JI Penghui1,2, QIAN Dan1,2, YANG Chengyun1,2, ZHANG Hongwei1,2,*()   

  1. 1 Henan Centre for Disease Control and Prevention, Zhengzhou 450016, China
    2 Henan Provincial Key Laboratory for Infectious Disease Prevention and Control, Zhengzhou 450016, China
    3 Children’s Hospital affiliated of Zhengzhou University; Henan Children’s Hospital; Zhengzhou Children’s Hospital, Zhengzhou 450000, China
    4 National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention (Chinese Center for Tropical Diseases Research); NHC Key Laboratory of Parasite and Vector Biology; WHO Collaborating Centre for Tropical Diseases; National Center for International Research on Tropical Diseases, Shanghai 200025, China
  • Received:2022-07-21 Revised:2023-01-23 Online:2023-06-30 Published:2023-06-15
  • Contact: *E-mail: zhwei69@163.com
  • Supported by:
    Henan Medical Science and Technology Plan Project(LHGJ20220178)

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Abstract:

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.

Key words: Giardia lamblia, Triosephosphate isomerase genes, Glutamate dehydrogenase gene, Beta-giardin gene, Phylogenetic analysis

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