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Blastocystis hominis and Dientamoeba fragilis in patients fulfilling irritable bowel syndrome criteria

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Studies have suggested a possible role for Blastocystis hominis and Dientamoeba fragilis in the etiology of irritable bowel syndrome (IBS). We studied the prevalence of B. hominis and D. fragilis in patients with IBS-diarrhea (IBS-D). Three hundred and thirty patients were enrolled, 171 (52%) with IBS-D and 159 (48%) were controls, respectively. Stool microscopy, culture, and polymerase chain reaction (PCR) for B. hominis and D. fragilis were done. B. hominis was positive by stool microscopy in 49% (83/171) of IBS compared to 24% (27/159) in control (p < 0.001). B. hominis culture was positive in 53% (90/171) in IBS compared to 16% (25/159) in control (p < 0.001). B. hominis PCR was positive in 44% (75/171) in IBS compared to 21% (33/159) in control (p < 0.001). D. fragilis microscopy was positive in 3.5% (6/171) in IBS-D compared to 0.6% (1/159) in control (p = 0.123). D. fragilis culture was positive in 4% (7/171) in IBS compared to 1.3% (2/159) in control (p = 0.176). D. fragilis PCR was positive in 4% (6/171) in IBS-D compared to 0% (0/159) in control (p = 0.030). B. hominis is common, while D. fragilis was less prevalent in our patients with IBS-D. B. hominis and D. fragilis culture had a better yield compared to stool microscopy and PCR.

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  • Brody TJ, Warren E, Wettstein A, Robertson P, Recabarren A (2002) Eradication of Dientamoeba fragilis can resolve IBS-like symptoms. J Gastroenterol Hepatol 17:A103

    Article  Google Scholar 

  • Dobell C (1940) Researches on the intestinal protozoa of monkeys and man. The life history of Dientamoeba fragilis: observations, experiments and speculations. Parasitology 32:417–461

    Article  Google Scholar 

  • Drossman DA (2006) Rome III: the new criteria. Chin J Dig Dis 7:181–185

    Article  PubMed  Google Scholar 

  • Eroglu F, Genc A, Elgun G, Koltas IS (2009) Identification of Blastocystis hominis isolates from asymptomatic and symptomatic patients by PCR. Parasitol Res 105:1589–1592

    Article  PubMed  Google Scholar 

  • Hussein EM, Hussein AM, Eida MM, Atwa MM (2008) Pathophysiological variability of different genotypes of human Blastocystis hominis Egyptian isolates in experimentally infected rats. Parasitol Res 102:853–860

    Article  PubMed  Google Scholar 

  • Hussain R, Jafri W, Zuberi S, Baqai R, Abrar N, Ahmed A, Zaman V (1997) Significantly increased IgG2 subclass antibody levels to Blastocystis hominis in patients with irritable bowel syndrome. Am J Trop Med Hyg 56:301–306

    CAS  PubMed  Google Scholar 

  • Johnson EH, Windsor JJ, Clark CG (2004) Emerging from obscurity: biological, clinical, and diagnostic aspects of Dientamoeba fragilis. Clin Microbiol Rev 17:553–570

    Article  PubMed  Google Scholar 

  • Norberg A, Nord CE, Evengard B (2003) Dientamoeba fragilis—a protozoal infection which may cause severe bowel distress. Clin Microbiol Infect 9:65–68

    Article  CAS  PubMed  Google Scholar 

  • Schuster H, Jackson RS (2009) Prevalence of Dientamoeba fragilis among patients consulting complementary medicine practitioners in the British Isles. J Clin Pathol 62:182–184

    Article  CAS  PubMed  Google Scholar 

  • Silberman JD, Clark CG, Sogin ML (1996) Dientamoeba fragilis shares a recent common evolutionary history with the trichomonads. Mol Biochem Parasitol 76:311–314

    Article  CAS  PubMed  Google Scholar 

  • Stark D, Beebe N, Marriott D, Ellis J, Harkness J (2005) Prospective study of the prevalence, genotyping and clinical relevance of Dientamoeba fragilis infections in an Australian population. J Clin Microbiol 43:2718–2723

    Article  CAS  PubMed  Google Scholar 

  • Stensvold CR, Brillowska-Dabrowska A, Nielsen HV, Arendrup MC (2006) Detection of Blastocystis hominis in unpreserved stool specimens by using polymerase chain reaction. J Parasitol 92:1081–1087

    Article  CAS  PubMed  Google Scholar 

  • Stensvold CR, Arendrup MC, Mølbak K, Nielsen HV (2007) The prevalence of Dientamoeba fragilis in patients with suspected enteroparasitic disease in a metropolitan area in Denmark. Clin Microbiol Infect 13:839–842

    Article  CAS  PubMed  Google Scholar 

  • Tan KSW (2008) New insights on classification, identification and clinical relevance of Blastocystis spp. Clin Microbiol Rev 21:639–665

    Article  CAS  PubMed  Google Scholar 

  • Windsor JJ, Johnson EH (1999) Dientamoeba fragilis: the unflagellated human flagellate. Br J Biomed Sci 56:293–306

    CAS  PubMed  Google Scholar 

  • Windsor JJ, Macfarlane L, Hughes-Thapa G, Jones SK, Whiteside TM (2002) Incidence of Blastocystis hominis in faecal samples submitted for routine microbiological analysis. Br J of Biomed Sc 59:154–157

    CAS  Google Scholar 

  • Windsor JJ, Macfarlane L, Hughes-Thapa G, Jones SK, Whiteside TM (2003) Detection of Dientamoeba fragilis by culture. Br J Biomed Sci 60:79–83

    CAS  PubMed  Google Scholar 

  • Yakoob J, Jafri W, Jafri N, Khan R, Islam M, Beg MA, Zaman V (2004) Irritable bowel syndrome: in search of an etiology: role of Blastocystis hominis. Am J Trop Med Hyg 70:383–385

    PubMed  Google Scholar 

  • Yakoob J, Jafri W, Beg MA, Abbas Z, Naz S, Islam M, Khan R (2010) Irritable bowel syndrome: is it associated with genotypes of Blastocystis hominis. Parasitol Res 106:1033–1038

    Article  PubMed  Google Scholar 

  • Yan Y, Su S, Ye J, Lai R, Liao H, Ye J, Li X, Luo X, Chen G (2006) Genetic variability of Blastocystis hominis isolates in China. Parasitol Res 99:597–601

    Article  PubMed  Google Scholar 

  • Yang J, Scholten TH (1977) Dientamoeba fragilis: a review with notes on its epidemiology, pathogenicity, mode of transmission and diagnosis. Am J Trop Med Hyg 26:16–22

    CAS  PubMed  Google Scholar 

  • Yoshikawa H, Abe N, Iwasawa M, Kitano S, Nagano I, Wu Z, Takahashi (2000) Genomic analysis of Blastocystis hominis strains isolated from two long-term Health care facilities. J Clin Microbiol 38:1324–1330

    CAS  PubMed  Google Scholar 

  • Zaman V, Khan K (1994) A comparison of direct microscopy with culture for the diagnosis of Blastocystis hominis. Southeast Asian J Trop Med Hyg Public Health 25:792–793

    Google Scholar 

  • Zonta ML, Oyhenart EE, Navone GT (2010) Nutritional status, body composition, and intestinal parasitism among the Mbyá-Guaraní communities of Misiones, Argentina. Am J Hum Biol 22:193–200

    CAS  PubMed  Google Scholar 

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This study was supported by the Higher Educational Commission Grant Ref: 20-774/R&D/06/267 to JY. We are thankful to Dr. C. Graham Clark (Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, England) for providing us the controlled DNA of D. fragilis cultures and to Dr. JJ Windsor (NPHS Microbiology Aberystwyth, Bronglais Hospital, Ceredigion, UK) for his valuable comments.

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Correspondence to Javed Yakoob.

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Yakoob, J., Jafri, W., Beg, M.A. et al. Blastocystis hominis and Dientamoeba fragilis in patients fulfilling irritable bowel syndrome criteria. Parasitol Res 107, 679–684 (2010).

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