Frequency and distribution of Blastocystis sp. subtypes in patients with spondyloarthritis in Bogotá, Colombia

Abstract

Although Blastocystis sp. is one of the most prevalent intestinal parasites worldwide, its role as a pathogen remains unclear. The use of molecular techniques to assess the genetic heterogeneity of Blastocystis sp. has become important to understand its function in some intestinal pathologies and if it is a key component of intestinal microbiota. Spondyloarthritis is a group of immune-mediated autoinflammatory diseases in which microbial dysbiosis in the gut (including parasites, bacteria and fungi) and intestinal inflammation are common features apparently associated with the pathophysiology of these disorders. This study included 74 patients diagnosed with spondyloarthritis and 57 systemically healthy individuals (included as controls), who were screened for intestinal parasites. Blastocystis sp. was detected in 68% and 73% of the patients with spondyloarthritis and controls, respectively. In faecal samples positive for Blastocystis sp., an 18S rRNA gene fragment of Blastocystis sp. was amplified and sequenced to identify their genetic sub-types. Patients with spondyloarthritis showed similar frequencies of ST1, ST2 and ST3 subtypes of Blastocystis sp. (30% each). The same subtypes were observed in controls, wherein almost 60% of the samples showed ST3. In addition, ST6 was found only in one sample from each group. ST1 subtype showed the greatest genetic variability. Although the same subtypes were detected in both patients with spondyloarthritis and controls, subtype prevalence studies conducted in Colombia indicate an association between ST3 and individuals with irritable bowel syndrome. This opens an interesting research avenue to further study of the epidemiology of Blastocystis sp. and its possible relationship with intestinal conditions in immunocompromised patients.

Keywords: Blastocystis; Colombia; Intestinal parasites; Spondyloarthritis; Subtypes.

Fig. 1

Frequency of Blastocystis sp. subtypes and alleles in spondyloarthritis (SpA) patients and controls. Frequency percentage values are relative to the total for each group, 23 sequences from controls and 17 sequences from SpA patients.

Fig. 2

Phylogenetic tree of 18S rRNA gene fragment of Blastocystis sp. samples. Constructed with the maximum likelihood method and the Tamura Nei model. Bootstrap values of >50% are shown for the nodes. Tree was constructed in MEGA X and edited using iTOL v5 (https://itol.embl.de/). Blastocystis sp. sequences of spondyloarthritis patients are shown in red and those of healthy controls in black. Reference subtype sequences retrieved from GenBank and ST4 sequence from DNA ATCC used as control are shown in bold type. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)