Comparative Prevalence of Blastocystis in Patients with the Irritable Bowel Syndrome and Healthy Individuals: A Case Control Study

Blastocystis is one of the most common anaerobic protozoa found in the intestinal tract of humans and various animals, with a worldwide distribution. The parasite has been linked to the pathogenesis of the irritable bowel syndrome (IBS), previously.
The aim of this study was to evaluate the prevalence of Blastocystis in IBS patients compared to healthy individuals.
The collected feces from 152 patients with Gastrointestinal (GI) symptoms, and 130 healthy volunteers from Ahvaz, southwest Iran, were examined using the direct saline smear, Lugol’s iodine staining, and inoculated in a Jones’ medium for Blastocystis detection. The DNA was extracted from all culture-positive samples, and then the polymerase chain reaction (PCR) was performed by the SSU-rDNA gene.
Blastocystis was identified in 18 (6.4%) samples, including two (1.3%) of the IBS patients and 16 (12.3%) of the control group by microscopy. Stool culture was positive in 15 with IBS, one without IBS, and 40 control samples. From these, the expected 600 bp fragments of the SSU-rDNA gene were identified in 15 (27.3%) cases and 40 (72.7%) controls. Subtypes (STs) 1, 2, and 3 were identified from the 54 successfully sequenced samples. Subtype 3 was the most common ST with the frequency of 46.3%, followed by ST2, 37% and ST1, 16.7% in the case and control groups. The highest frequency of Blastocystis STs (27.8%) was identified in the age group of 31-40 years and the lowest was found in the age groups of under 10 years and over 81 years.
The findings of the current study showed that Blastocystis was more common in the control group compared to the IBS patients. Therefore, our findings highlight the contrast between Blastocystis infection and GI disorders. Furthermore, these results support the hypothesis that Blastocystis could be a GI health marker.