Frequency, Associated Factors, Clinical Symptoms, and Subtypes of Blastocystis sp. in Patients With Irritable Bowel Syndrome and Healthy Individuals: A Case-Control Study

Blastocystis sp. is a widespread gastrointestinal inhabitant in human fecal samples that may present with diarrhea, vomiting, stomachache, and even irritating bowel syndrome (IBS). The probable association between Blastocystis infection and IBS has been the focus of many recent studies.

The current study investigated the frequency, associated risk factors, clinical symptoms, and subtypes of Blastocystis sp. among IBS and control individuals.

In total, 202 stool samples (101 IBS patients and 101 control group) were collected upon giving consent. In addition, a questionnaire was completed by individuals, including demographic information. Fecal examination was performed using the direct microscopic, culture (DMEM), and molecular method.

The mean±standard deviation for the age of the involved subjects was 40.86±15.36 and 38.89±15.57 in the case and control groups, respectively. Further, among IBS patients and the control group, 53 (52.48%) and 50 (49.51%) were males and 48 (47.52%) and 51 (50.49%) were females, respectively. There was no statistically significant difference between the two groups in terms of age and gender (P>0.05). In this study, 35 (17.32%), 68 (33.66%), and 62 (30.69%) using direct, culture, and molecular methods, respectively, were positive regarding Blastocystis sp., and no statistically significant difference was observed in this regard (P>0.05). Based on molecular findings, subtypes 1 (21.28%) and 3 (6.93%) were the most common in both groups, which did not demonstrate a statistical significance (P>0.05).

In general, although the predominant subtype in the IBS group is subtype 1, this difference between the case and control groups was not statistically significant. Specific subtypes of Blastocystis have only been associated with gut dysbiosis. The accurate diagnosis of this parasite, especially at the phenotypic and genotypic levels, along with its correlation with the gut microbiota, should be considered in future studies on IBS patients.