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Published on: May 26, 2026
High resolution multi-locus sequence typing scheme for Giardia duodenalis assemblage B outbreak and population
Christian Klotz1, Katja Winter2, Marc W Schmid3
1Department of Infectious Diseases, Unit for Mycotic and Parasitic Agents and Mycobacteria, Robert Koch-Institute, Berlin, Germany.
Plos Neglected Tropical Diseases
|July 15, 2026
Summary
A new multi-locus sequence typing (MLST) scheme effectively differentiates Giardia duodenalis assemblage B strains. This tool aids in tracking giardiasis outbreaks and identifying infection sources by analyzing allelic sequence heterogeneity (ASH).
Area of Science:
- Parasitology
- Molecular Epidemiology
- Genomics
Background:
- Giardia duodenalis is a protozoan parasite causing human giardiasis, a common gastrointestinal illness.
- Assemblages A and B are the primary groups responsible for human infections, exhibiting distinct genetic characteristics.
- Accurate typing schemes are crucial for epidemiological investigations, including outbreak tracing and source attribution of Giardia duodenalis assemblage B.
Purpose of the Study:
- To identify genomic markers for molecular typing of Giardia duodenalis assemblage B.
- To develop and evaluate a novel multi-locus sequence typing (MLST) scheme for assemblage B.
- To assess the utility of the MLST scheme in distinguishing between epidemiologically related and unrelated isolates.
Main Methods:
- Whole genome datasets from 18 axenically cultured Giardia duodenalis assemblage B isolates were analyzed.
- Genomic loci were identified, and primer sets were designed for nested PCR and sequencing.
- A seven-marker MLST scheme was developed and applied to 146 assemblage B samples, including analysis of allelic sequence heterogeneity (ASH).
Main Results:
- The developed MLST scheme successfully genotyped 75% (109/146) of tested Giardia duodenalis assemblage B samples.
- Analysis of epidemiologically unrelated samples revealed a bipartite population structure based on low or high ASH.
- Samples from a waterborne outbreak and epidemiologically linked cases formed distinct clusters, differentiating them from sporadic cases.
Conclusions:
- The novel MLST scheme is informative for molecular typing of Giardia duodenalis assemblage B.
- The scheme effectively distinguishes between different genetic profiles within assemblage B, including those with varying ASH.
- This tool can significantly assist in future epidemiological studies, outbreak investigations, and source attribution of Giardia duodenalis assemblage B.
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