Investigation of Dientamoeba fragilis with microscopical and molecular methods in patients with ulcerative colitis and irritable bowel syndrome, genotyping and cysteine peptidase virulence factor

Dientamoeba fragilis is a common intestinal protozoon whom pathogenicity is still debated. Two genotypes of this parasite have been determined, Genotype 1 is common worldwide. Microscopy, culture and molecular methods are used for diagnosis. The aim of this study is to investigate D. fragilis in patients with active and remittent ulcerative colitis (UC) and irritabl bowel syndrome (IBS) by different diagnostic methods and investigate its genotypes. There is not any published data on the genotypes of D. fragilis in Turkey. The stool samples were investigated microscopically by saline-Lugol and trichrome staining methods. All samples were scanned for D. fragilis via conventional, nested and qPCR method. Blastocystis spp were investigated by conventional PCR. Positive samples were genotyped via sequencing with BLAST algorithm. Our results revealed that 4 IBS, 2 active UC and 2 remittent UC patients were infected with D. fragilis, whereas 3 IBS, 5 active UC and 1 remittent UC patients were infected with Blastocystis spp. One active UC and one IBS patient were infected with both of the parasites. The difference between the groups were not statistically significant. All D. fragilis isolates were Genotype 1 and Blastocystis isolates were ST3. Cysteine, serine and metallopeptidase virulence genes were investigated by nested-PCR and 6 of the isolates were found to be positive. Nested PCR, with its 75% of sensitivity was concluded to be an alternative to qPCR which is the golden method for the identification of D. fragilis.