Genetic characterization of Blastocystis spp. in patients with colorectal cancer, irritable bowel syndrome, and asymptomatic individuals in Sohag, Egypt

Abstract

Background: Blastocystis spp. is common protozoan parasite and show extensive genetic diversity with 16 different subtypes (STs) have been identified in humans. Objective: The aim of this study was to determine the prevalence and subtypes of Blastocystis spp. in colorectal cancer (CRC) patients, irritable bowel syndrome (IBS) patients and asymptomatic individuals in Sohag, Egypt. Methods: A cross-sectional study was conducted on 225 stool samples collected from 75 CRC patients, 75 IBS patients and 75 asymptomatic individuals. All samples were examined microscopically by direct smears, FECT and cultured on modified Jones’ medium supplemented with 10% donkey serum. The genomic DNA was extracted from positive stool samples. Conventional and nested PCRs (nPCR) were used to amplify of small-subunit ribosomal RNA (SSU rRNA) gene of Blastocystis spp. Subtypes were identified by RFLP of nested PCR products using Hinf I and Rsa I. Results: Out of 225 stool samples, Blastocystis was detected in 97 samples (43.1%) by culture, 89 samples (39.6%) by direct smears and 71 samples (31.6%) by FECT with significant difference (P=0.035). The sensitivity of direct smears and FECT compared to culture was 87.6% and 73.2% while the specificity was 96.9% and 100% respectively. The prevalence of Blastocystis spp. was significantly higher in CRC patients (53.3%) and IBS group (48%) than in asymptomatic participants (28%) (P =0.004). Out of 97 positive fecal samples, Blastocystis SSU rRNA gene was amplified in 45 samples by conventional PCR and 95 samples by nPCR. RFLP analysis identified three STs. ST3 was the most common followed by ST1 and ST2 However, there was no significant difference between Blastocystis STs and socio-demographic and clinical groups of participants. Conclusions: The prevalence of Blastocystis spp. was higher in CRC patients and IBS patients than in asymptomatic group and ST3 was the most prevalent subtype in study groups.