Molecular Identification, Subtypes Distribution, and Alleles Discrimination of Blastocystis sp., Isolated from Immunocompromised Subjects in Iran

Blastocystis sp., is a prevalent protist isolated from humans and animals, which its opportunistic role in immunocompromised patients is still controversial. The current study aimed to evaluate the subtype and alleles distribution of Blastocystis sp., among immunocompromised patients.

Totally, 33 microscopically Blastocystis-positive stool samples, isolated from Guilan province during April 2018 to May 2019 were investigated. Total DNA extraction was performed and the barcoding region of the small subunit ribosomal RNA (SSU rRNA) gene was amplified. Targeted fragments were sequenced to characterize subtypes and relevant alleles. Phylogenetic tree was constructed using Maximum-likelihood and Tamura 3-parameter to illustrate the correlation between subtypes and certain immunodeficiency.

Subtype analysis revealed the presence of ST1, ST2, ST3, and ST7 among 13/33 (39.4%), 5 (15.2%), 14/33 (42.4%), and 1/33 (3%), of samples, respectively. ST1 was the major subtype among cancer patients 5/7 (71.42%), while ST3 was the predominant subtype among rheumatoid arthritis (RA) patients 3/6 (50%), internal ward patients 5/10 (50%), and asthma and allergy patients 2/3 (66.66%). ST7 was isolated from a patient hospitalized in internal ward. No significant correlation was seen between the type of immunodeficiency and subtypes (P-value = 0.771). The phylogenetic tree showed no separation regarding the type of immunodeficiency.

Among studied immunocompromised patients, ST3 was the most prevalent subtype followed by ST1. There was no specific correlation between subtypes and alleles with type of immunodeficiency. Putative zoonotic alleles were highlighted the probability of zoonotic transmission for Blastocystis sp.