Subtypes identification and frequency of Blastocystis isolated from patients in Kashan, Central Iran

 Blastocystis species are one of the most common enteric protist infections in humans and some animals worldwide. Molecular studies have shown that there is a high level of genetic variation among Blastocystis isolates. The aim of this study was to identify the subtypes and frequency of Blastocystis isolates in patients who referred to the medical diagnostic laboratories in Kashan, Central Iran. 

 This cross-sectional study was conducted on 1118 patients, from December 2017 to June 2018. Fecal specimens were evaluated by the microscopic examination. Positive samples were cultivated in Robinson media. After massive growth and DNA extraction, a 550 bp from the small subunit ribosomal RNA gene was amplified by the polymerase chain reaction (PCR) for subtype identification. The PCR products have been sequenced, identified, and compared at the NCBI site. The results were analyzed using the SPSS software version 16. 

 The frequency of Blastocystis sp. was 8.58%, (confidence interval = 6.94%–10.22%) from which 76% were men and 24% were women. Of the 51 PCR positive samples, ST3 (41.2%), ST1 (39.2%), ST2 (11.8%), and 7.8% isolates were identified as mixed. ST3 and ST1 have been more common. The highest levels of infection were observed in the food-handlers, the age group of 31–40, and people with high school education. 

 The results showed that the frequency of Blastocystis was lower than other studies and the most common Blastocystis subtype was subtype 3, followed by subtype 1, and subtype 2.