The Investigation of Blastocystis Frequency and Subtypes in Routine Laboratory Faecal Samples

Abstract

Blastocystis is a zoonotic protist that colonizes the human colon and has been widely studied in recent years, with particular focus on its genetic diversity and pathogenicity. Molecular epidemiology studies in different regions provide an opportunity to investigate the distribution of Blastocystis in society and its associated factors. This study aimed to evaluate the frequency of Blastocystis, subtype (ST) distribution and clinical findings in stool samples obtained from a routine laboratory. In the study, stool samples sent to Afyonkarahisar Health Sciences University Faculty of Medicine, Microbiology Laboratory for routine parasitology examination were evaluated. The presence of Blastocystis was investigated initially with direct microscopy (DM) of 252 faecal samples collected in two months. Genomic DNA was isolated from all stool samples and Blastocystis positivity was determined with polymerase chain reaction (PCR). STs were determined through databases and phylogenetic analysis based on the partial sequences of Blastocystis small subunit ribosomal ribonucleic acid (SSU rRNA) gene. In addition, the presence of possible mixed STs was further studied using ST-specific primers. The age, gender, location, clinical findings, enteric adenovirus and rotavirus positivity of the cases were statistically evaluated. Blastocystis forms were detected in 11 (4.3%) of the 252 faecal samples with DM method and 16 samples (6.3%) were positive with PCR. After sequence analysis, ST distribution was detected as follows: ST3 (nine isolates, 56.2%), ST2 (four isolates, 25%) and ST1 (three isolates, 18.8%). Mixed STs were not found in any of the samples. There was no statistically significant difference between women (5.8%) and men (6.8%) in terms of Blastocystis positivity (p> 0.05). However, the average age of Blastocystis positive cases was statistically higher than that of negative cases (p< 0.05). Enteric adenovirus and rotavirus positivity were examined using an immunochromatographic rapid diagnostic test in 172 cases. All of them were negative for adenovirus and 19 (11%) were positive for rotavirus. When clinical findings were evaluated with Blastocystis positivity, no significant difference was detected. In our study, the ST distribution of Blastocystis appeared to be compatible with those reported from other regions. When the clinical findings were evaluated, the idea of asymptomatic colonization of Blastocystis was also supported by this study.The combined use of more than one method in Blastocystis diagnosis increases the chance of detecting positive samples. It is highly believed that comprehensive studies about the coexistence of Blastocystis and viral factors, including the microbiota, are expected to provide valuable contributions to Blastocystis pathogenicity.