Dientamoeba fragilis dominance in IBS and Blastocystis sp. in ulcerative colitis.

Intestinal diseases markedly impair quality of life, with irritable bowel syndrome (IBS), ulcerative colitis (UC), and Crohn's disease (CD) representing major functional and inflammatory gastrointestinal disorders. This study aimed to determine the prevalence of Dientamoeba fragilis and other intestinal parasites in these conditions and to compare the diagnostic performance of conventional and molecular methods. A total of 80 stool samples were analyzed, including 60 from patients with IBS, UC, or CD and 20 from healthy controls. Samples were examined using direct microscopy, concentration techniques, trichrome staining (TS), and real-time polymerase chain reaction (qPCR), which was applied specifically for the detection of D. fragilis. Overall, parasites were detected in 60% of patients and 15% of controls. Infection rates were 33.3% in CD, 68.8% in UC, and 58.5% in IBS patients. D. fragilis was identified in 18.8% of UC and 22.0% of IBS cases, with significant differences observed between microscopy, TS, and qPCR in detection rates. Blastocystis sp. was found in 21.7% of patients and 5% of controls, with the highest prevalence in UC patients (37.5%). Other detected parasites included Iodamoeba bütschlii, Endolimax nana, Entamoeba coli, Giardia intestinalis, Chilomastix mesnili, Entamoeba spp., and Cystoisospora belli. While direct microscopy showed limited sensitivity, TS improved detection moderately, and qPCR provided the highest sensitivity for D. fragilis. These findings highlight the predominance of D. fragilis in IBS and Blastocystis sp. in UC and underscore the importance of molecular methods for accurate parasitological diagnosis.