title: The distribution of Blastocystis subtypes in isolates from Qatar.
abstract: BACKGROUND
  Blastocystis is a common single-celled intestinal parasite of humans and other animals comprising at least 17 genetically distinct small subunit ribosomal RNA lineages (subtypes (STs)), nine of which have been found in humans. The geographic distribution of Blastocystis subtypes is variable, but the subtypes present in Qatar are at present unknown.
  
  
  METHODS
  Stool samples were collected from randomly selected, apparently healthy subjects arriving in Qatar for the first time. Blastocystis subtypes were determined by sequencing of the small subunit rRNA gene (SSU rDNA) PCR products. Phylogenetic analyses were done using Maximum Composite Likelihood method.
  
  
  RESULTS
  71.1 % of samples were positive for Blastocystis infection based on PCR-detection methodology compared to only 6.9 % by microscopy. Prevalence of Blastocystis did not differ between the sexes nor between age classes. However, there was a regional difference in prevalence with subjects arriving from Africa showing the highest (87.6 %), those from Western Asia intermediate (68.6 %) and from Eastern Asia the lowest prevalence (67.6 %). Genetic analysis detected only three STs. ST3 was the most common (69.3 %) and ST2 was the rarest (3.5 %), while ST1 had a prevalence of 27.2 %. ST2 showed a regional variation, being absent from the 64 Western Asian Blastocystis-positive subjects. Both ST1 and ST3 showed significant differences in prevalence between the sexes.
  
  
  CONCLUSIONS
  This is the first report exploring the distribution of Blastocystis subtypes in our region. We recommend that stool screening via microscopy for the presence of Blastocystis should be abandoned since it is extremely insensitive. In future, the prevalence of Blastocystis infections should be based on PCR methodology and we predict that in the years ahead diagnostic PCR will become the tool of choice. More work is needed to identify the full range of Blastocystis subtypes that circulate in our region.
authors.affiliation: Department of Health Sciences, College of Arts and Science, Biomedical Research Center, Qatar University, P.O. Box 2713, Doha, Qatar. abumadi@qu.edu.qa.
authors.forename: Marawan
authors.initials: M
authors.lastname: Abu-Madi
authors.affiliation: King Abdullah International Medical Research Center, National Guard Health Affairs, Mail Code: 2216, P.O. Box 22490, Riyadh, 11426, KSA. alyma@ngha.med.sa.|King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia. alyma@ngha.med.sa.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Aly
authors.affiliation: School of Life Sciences, University of Nottingham, University Park, Nottingham, United Kingdom, NG7 2RD. Jerzy.Behnke@nottingham.ac.uk.
authors.forename: Jerzy M
authors.initials: JM
authors.lastname: Behnke
authors.affiliation: Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, London, United Kingdom. graham.clark@lshtm.ac.uk.
authors.forename: C Graham
authors.initials: CG
authors.lastname: Clark
authors.affiliation: King Abdullah International Medical Research Center, National Guard Health Affairs, Mail Code: 2216, P.O. Box 22490, Riyadh, 11426, KSA. balkhyh@hotmail.com.|King Saud bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia. balkhyh@hotmail.com.
authors.forename: Hanan
authors.initials: H
authors.lastname: Balkhy
mesh_terms: D000293:Adolescent; D000328:Adult; D016844:Blastocystis / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D016776:Blastocystis Infections / Q000175:diagnosis / Q000469:parasitology*; D016000:Cluster Analysis; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005243:Feces / Q000469:parasitology; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques / Q000639:trends; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000639:trends; D011780:Qatar; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D017422:Sequence Analysis, DNA; D055815:Young Adult
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S