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Multi-locus genotyping of Giardia intestinalis in Ugandan children with and without Helicobacter pylori colonization
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Microbiology. (Prof. Staffan Svärd)
2012 (English)In: PLoS Neglected Tropical Diseases, ISSN 1935-2735Article in journal (Other academic) Submitted
Abstract [en]


The protozoan parasite Giardia intestinalis and the pathogenic bacterium Helicobacter pylori are well known for their high prevalences in human hosts world-wide. The prevalence of both organisms is known to peak in densely populated, low resource settings and children are infected early in life. Different Giardia genotypes/assemblages have been associated with different symptoms and H. pylori with induction of cancer. Despite this, little data is available from sub-Saharan Africa with regards to the prevalence of different G. intestinalis assemblages and their potential association with H. pylori infections.

Methodology/Principal findings

Fecal samples from 427 apparently healthy children, 0-12 years of age, living in urban Kampala, Uganda were analyzed for the presence of H. pylori and G. intestinalis. G. intestinalis was found in 86 (20.1%) out of the children and children age 1<5 years had the highest rates of colonization. No significant association was found in the studied population with regards to the presence of Giardia and gender, type of toilet, source of drinking-water or type of housing. H. pylori was found in 189 (44.3%) out of the 427 children and there was a 3-fold higher risk of concomitant G. intestinalis and H. pylori infections compared to non-concomitant G. intestinalis infection, OR = 2.9 (1.7-4.8). A panel of 45 G. intestinalis positive samples was further analyzed using multi-locus genotyping (MLG) on the β-giardin (bg), glutamate dehydrogenase (gdh) and triosephosphate isomerase (tpi) loci, combined with assemblage-specific analyses. Giardia MLG analysis yielded a total of five assemblage A, 25 assemblage B, and four mixed assemblage infections. The assemblage B isolates were highly genetically variable and a significant association was found between Giardia assemblage B and H. pylori infection, OR=5.0 (1.9- 16).


This study shows that Giardia assemblage B dominates in children in Kampala, Uganda and that Giardia-infected children have a 3-fold higher risk of being infected by H. pylori. The data also suggests that assemblage B Giardia may be more closely associated with H. pylori infection.

Place, publisher, year, edition, pages
National Category
Medical and Health Sciences Natural Sciences
Research subject
Molecular Medicine
URN: urn:nbn:se:uu:diva-167046OAI: oai:DiVA.org:uu-167046DiVA: diva2:480601
Available from: 2012-01-19 Created: 2012-01-19 Last updated: 2012-02-15Bibliographically approved
In thesis
1. Inter and Intra-Assemblage Characterizations of Giardia intestinalis: from clinic to genome
Open this publication in new window or tab >>Inter and Intra-Assemblage Characterizations of Giardia intestinalis: from clinic to genome
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The protozoan parasite Giardia intestinalis (syn. G. lamblia, G. duodenalis) is one of the most common causes of diarrheal disease throughout the world, where an estimated 500 million people are infected annually. Despite efforts in trying to elucidate factors associated with virulence in G. intestinalis little is currently known. The disease outcome is highly variable in Giardia infected individuals, ranging from asymptomatic carriers to severe disease. The reasons behind the differences in disease outcome are vaguely understood and studies trying to link infectivity to different Giardia assemblages or sub-assemblages have rendered conflicting results. Prior to this study, little was known about the prevalence and genetic diversity of different G. intestinalis assemblages across the world.

In this thesis, molecular characterization of clinical G. intestinalis samples from Eastern Africa and Central America, has been performed, enabling a better understanding of the prevalence of different Giardia genotypes in endemic areas (Papers I and II). A correlation between Giardia colonization and the presence of Helicobacter pylori in the human host was established. We found that the currently available genotyping tools provide low resolution when used to characterize assemblage A Giardia. Also, genotyping of assemblage B isolates at these loci is troublesome due to the polymorphic substitutions frequently found in the sequencing chromatograms. This ambiguity was investigated by using micromanipulation to isolate single assemblage B Giardia cells (Paper III). Both cultured trophozoites and cysts from giardiasis patients were analyzed. The data showed that allelic sequence heterozygosity (ASH) does occur at the single cell level, but also that multiple sub-assemblage infections appear to be common in human giardiasis patients.

Furthermore, genome-wide sequencing followed by comparative genomics was performed in order to better characterize differences between and within different Giardia assemblages. The genome of a non-human infecting, assemblage E isolate (Paper IV) was sequenced.  The genomes of two freshly isolated human infecting assemblage AII isolates were also sequenced (Paper V). Subsequent, comparative analyses were performed and included the genomes of two human infecting isolates, WB (AI) and GS/M (B). Several important differences were found between assemblages A, B and E, but also within assemblage A; including unique gene repertoires for each isolate, observed differences in the variable gene families and an overall difference in ASH between the different isolates. Also, a new multi-locus genotyping (MLG) strategy for genotyping of assemblage A Giardia has been established and evaluated on clinical samples from human giardiasis patients.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 85 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 893
Giardia, protozoa, parasite infection, diarrhea, genome sequencing, comparative genomics, genotyping, ASH, MLG
National Category
Natural Sciences Medical and Health Sciences
Research subject
Infectious Diseases; Molecular Medicine; Microbiology
urn:nbn:se:uu:diva-167063 (URN)978-91-554-8259-6 (ISBN)
Public defence
2012-02-23, B42, BMC, Husargatan 3, Uppsala, 10:15 (English)
Available from: 2012-02-02 Created: 2012-01-19 Last updated: 2012-02-15Bibliographically approved

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