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Subtype analysis of Blastocystis isolates in Swedish patients
Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Infectious Diseases. Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Clinical Bacteriology.
Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
Umeå University, Faculty of Medicine, Department of Clinical Microbiology.
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2012 (English)In: European Journal of Clinical Microbiology and Infectious Diseases, ISSN 0934-9723, E-ISSN 1435-4373, Vol. 31, no 7, 1689-1696 p.Article in journal (Refereed) Published
Abstract [en]

Blastocystis is a genetically diverse and widespread intestinal parasite of animals and humans with controversial pathogenic potential. At least nine subtypes of Blastocystis have been found in humans. The genetic diversity of Blastocystis was examined in stool samples from 68 patients from the Stockholm area, Sweden. Blastocystis was identified by light microscopy, and subtyped by sequencing the 5'-end of the small subunit ribosomal RNA gene. Five Blastocystis subtypes were identified in the 63 patients whose samples were successfully subtyped: ST1 (15.9%), ST2 (14.3%), ST3 (47.6%), ST4 (20.6%), and ST7 (1.6%). ST3 was more common in males compared to females (P = 0.049). Comparative molecular analysis of Blastocystis sequences revealed intra-subtype variations within the identified subtypes with the exception of ST4. Among ST4 sequences in this study, as well as in the majority of human GenBank sequences, a limited genetic diversity was found compared to what was found among the other common subtypes (ST1, ST2 and ST3). The relative prevalence of ST4 in this study was comparable to the overall distribution of ST4 in European cohorts (16.5%). This contrasts with the sparse reports of ST4 in studies from other continents, which may indicate that the distribution of this subtype is geographically heterogeneous.

Place, publisher, year, edition, pages
Heidelberg: Springer Berlin/Heidelberg, 2012. Vol. 31, no 7, 1689-1696 p.
National Category
Microbiology in the medical area
Identifiers
URN: urn:nbn:se:umu:diva-56679DOI: 10.1007/s10096-011-1416-6ISI: 000304652800052PubMedID: 22350386OAI: oai:DiVA.org:umu-56679DiVA: diva2:537705
Available from: 2012-06-27 Created: 2012-06-25 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Genetic subtypes in unicellular intestinal parasites with special focus on Blastocystis
Open this publication in new window or tab >>Genetic subtypes in unicellular intestinal parasites with special focus on Blastocystis
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of molecular tools for detection and typing of unicellular intestinal parasites has revealed genetic diversities in species that were previously considered as distinct entities. Of great importance is the genetic distinction found between the pathogenic Entamoeba histolytica and the non-pathogenic Entamoeba dispar, two morphologically indistinguishable species. Blastocystis sp. is a ubiquitous intestinal parasite with unsettled pathogenicity. Molecular studies of Blastocystis sp. have identified 17 genetic subtypes, named ST1-17. Genetically, these subtypes could be considered as different species, but it is largely unknown what phenotypic or pathogenic differences exist between them. This thesis explores molecular methods for detection and genetic subtyping of unicellular intestinal parasites, with special focus on Blastocystis.

We found that PCR-based methods were highly sensitive for detection of unicellular intestinal parasites, but could be partially or completely inhibited by substances present in faeces. A sample transport medium containing guanidinium thiocyanate was shown to limit the occurrence of PCR inhibition.

The prevalence of Blastocystis in Swedish university students was over 40%, which is markedly higher than what was previously estimated. Blastocystis ST3 and ST4 were the two most commonly found Blastocystis subtypes in Sweden, which is similar to results from other European countries.

Blastocystis sp. and Giardia intestinalis were both commonly detected in Zanzibar, Tanzania, each with a prevalence exceeding 50%. Blastocystis ST1, ST2, and ST3 were common, but ST4 was absent. While G. intestinalis was most common in the ages 2-5 years, the prevalence of Blastocystis increased with increasing age, at least up to young adulthood. We found no statistical association between diarrhoea and Blastocystis sp., specific Blastocystis subtype or G. intestinalis.

Metagenomic sequencing of faecal samples from Swedes revealed that Blastocystis was associated with high intestinal bacterial genus richness, possibly signifying gastrointestinal health. Blastocystis was also positively associated with the bacterial genera Sporolactobacillus and Candidatus Carsonella, and negatively associated with the genus Bacteroides.

Blastocystis ST4 was shown to have limited intra-subtype genetic diversity and limited geographic spread. ST4 was also found to be the major driver behind the positive association between Blastocystis and bacterial genus richness and the negative association with Bacteroides.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2017. 61 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1889
Keyword
Intestinal parasites, Blastocystis, Entamoeba, Giardia, molecular detection, PCR, subtype, intestinal microbiota, Sweden, Zanzibar
National Category
Microbiology in the medical area Infectious Medicine
Research subject
Clinical Bacteriology
Identifiers
urn:nbn:se:umu:diva-132441 (URN)978-91-7601-682-4 (ISBN)
Public defence
2017-04-07, Hörsal D, byggnad 1D, Norrlands universitetssjukhus, Umeå, 09:00 (English)
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Supervisors
Available from: 2017-03-17 Created: 2017-03-14 Last updated: 2017-03-15Bibliographically approved

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Forsell, JoakimGranlund, MargaretaStensvold, C. R.Clark, G. C.Evengård, Birgitta
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