The identification of blastocystis subtypes by sequencing in Adnan Menderes University, Faculty of Medicine parasitology laboratory

The aim of this study was to determine subtype distribution of Blastocystis isolates from Adnan Menderes University, Parasitology Laboratory. Moreover, it was aimed to evaluate direct microscopy (DM), culture and polymerase chain reaction (PCR). Finally, we aimed to analyse clinical findings in relation to Blastocystis infection, retrospectively. A total of 200 faecal samples were selected with DM (100 positive and 100 negative). All were cultured and studied with PCR. Subtypes were determined by sequencing of the partial small sub-unit ribosomal RNA gene of Blastocystis (all of faecal samples and some of culture positives). The samples, which were not able to be subtyped by sequencing were further studied with sequence tagged site-PCR (STS-PCR). Finally, the clinical findings between Blastocystis infected and non-infected cases as well as subtypes were compared. Of the 100 DM positive samples 81 (81%) were positive with culture and 86 (86%) were positive with PCR. Additionally, positivity was five (5%) and seven (7%) with culture and PCR in DM negative group, respectively. Subtypes of 95 isolates were determined by sequencing or STS-PCR, the distribution was as follows: ST3 (n=50, 52,6%), ST2 (n=21, 22,1%), ST1 (n=17, 17,9%), ST7 (n=4, 4,2%), ST2+ST3 (n=2, 2,1%) and ST1+ST3 (n=1, 1,1%). There was no statistically significant difference between Blastocystis positive and negative groups in terms of any symptoms and also subtypes. In conclusion, direct microscopy seems to be an ineffective method for Blastocystis diagnosis as it causes false negativity and positivity. Thus it would be useful to use additional diagnostic tools such as culture or PCR. The subtype distribution of Blastocystis in Aydin was in accordance with the previous data, globally. Finally, our clinical findings support the idea of asymptomatic colonization of Blastocystis in human gut and being a flora member.