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Dominance of Giardia assemblage B in León, Nicaragua.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
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2008 (English)In: Acta Tropica, ISSN 0001-706X, E-ISSN 1873-6254, Vol. 106, no 1, 44-53 p.Article in journal (Refereed) Published
Abstract [en]

Giardiasis is a major problem in León, Nicaragua, yet despite this no data are available regarding the prevalence of different Giardia genotypes in this area. To address this question, a molecular analysis of Giardia isolates from humans and dogs living in the same area in León, Nicaragua was performed. Giardia isolates from 119 Nicaraguan patients and 8 dogs were successfully genotyped using single and/or nested beta-giardin PCR with subsequent restriction length fragment polymorphism (RFLP) analysis. The analyses of human samples yielded 94 (79%) assemblage B isolates and 25 (21%) assemblage A isolates. Only the non-human-associated assemblages C and D were found in the dog samples. Sixteen isolates with assemblage A pattern, 26 isolates with assemblage B pattern and all dog isolates were further characterized by sequencing the nested beta-giardin PCR product and by molecular analyses of the glutamate dehydrogenase (gdh) gene. Within the study area the assemblage A isolates were highly genetically homogenous, showing only sub-genotypes A2 (n=3) or A3 (n=13) at the beta-giardin locus and AII only at the gdh locus while assemblage B showed a high genetic polymorphism at both loci. Seven different sub-genotypes were identified within 13 of the sequenced assemblage B beta-giardin isolates. The remaining 13 sequenced assemblage B-isolates appeared to contain several different variants of the beta-giardin gene since the chromatograms displayed one to seven double peaks. The gdh sequences showed an even higher polymorphism since only 2 of 26 assemblage B isolates were without double peaks. Two mixed infections between assemblage A and B were found when the gdh gene was analyzed. Polymorphisms were also observed in the dog-associated assemblages C and D, but to a lesser extent than in assemblage B.

Place, publisher, year, edition, pages
2008. Vol. 106, no 1, 44-53 p.
Keyword [en]
Nicaragua, Giardia intestinalis, (-Giardin gene, glutamate dehydrogenase gene, genotyping, diarrhea
National Category
Biochemistry and Molecular Biology
URN: urn:nbn:se:uu:diva-16512DOI: 10.1016/j.actatropica.2008.01.004ISI: 000255487100007PubMedID: 18325480OAI: oai:DiVA.org:uu-16512DiVA: diva2:44283
Available from: 2008-05-27 Created: 2008-05-27 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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