Suitability of internal transcribed spacers (ITS) as markers for the population genetic structure of Blastocystis spp

Abstract

Background: The purpose of this study was to assess the genetic variation and differentiation of Blastocystis subtypes (STs) recovered from symptomatic children by analysing partial sequences of the small subunit rDNA gene region (SSUrDNA) and internal transcribed spacers (1 and 2) plus the 5.8S region (ITS, ITS1 + 5.8S + ITS2) and comparing with isolates from other countries.

Clarifying the Cryptic Host Specificity of Blastocystis spp. Isolates from Alouatta palliata and A. pigra Howler Monkeys

“…The high degree of intra-ST genetic polymorphism has been reliably documented, particularly for ST1 and ST3 [12, 14, 16, 41, 43–44], suggesting that populations of recent origin have undergone a radiation process [52]. However, the great divergence of some haplotypes for ST1 and ST2 observed in the present study deserves special attention.…”

“…Subsequently, in another study performed in similar populations of these howler monkeys, 68% of these animals were infected with Blastocystis ST8, while humans living in close proximity were infected with ST1, ST2 and ST3 [15]. Interestingly, although these subtypes (ST1-ST3) are distributed worldwide, they are common in America [8, 40, 41]. In the present study, 39% and 38% of A .…”

“…Genetic diversity analyses within and between populations were performed using DnaSPv4 [39], and indices, such as nucleotide diversity (π), haplotype polymorphism (θ), gene flow ( Nm ),genetic differentiation index (F ST ) and Tajima’s D test were obtained. These indices have been previously applied for population genetics studies in Blastocystis [40, 41]. They denote the average proportion of nucleotide differences between all possible pairs of sequences in the sample (π); the proportion of nucleotide sites expected to be polymorphic in any suitable sample from this region of the genome (θ); the movement of organisms among subpopulations ( Nm ); and the differentiation between or among populations (F ST ).…”

Blastocystis and urticaria: Examination of subtypes and morphotypes in an unusual clinical manifestation

“…Domesticated mammals shared the same STs as those usually seen in humans (ST1, ST2, ST3), while birds and marsupials had STs, which are usually rare in humans (ST6, (Ramírez et al, 2014). In Brazil, ST1 (41%), ST2 (32%) and ST3 (17%) were identified in an ethnic group (Malheiros et al, 2011) in Mexico a local survey identified 51% of ST1, 23% of ST2, 19% of ST3 and 2% of ST7 (Villalobos et al, 2014). Despite of the initial descriptions of this protozoan in the early 1900s, there is scarce information and misleading assumptions regarding the pathogenesis of this Stramenophile (Tan, 2008).…”

“…Although dramatic differences are seen across regions Q6 (Ramírez et al, 2014;Rivera, 2008), the distribution of STs in our samples demonstrated that ST3 was the most frequently detected ST, followed by STs 1, 6 and 2; these findings are similar to those previously reported in the Americas . The presence of ST6 is of interest, because particularly this subtype has been only detected in wild animals but not in humans across South America (Ramírez et al, 2014;Malheiros et al, 2011;Villalobos et al, 2014) and the fact that ST6 in Europe represents one of the STs identified in human samples might reflect the European genetic background present in Argentinean populations or vast migrant flow among these areas suggesting that host-factors might play a relevant role on the pathogenesis adaptation of Blastocystis infection. An interesting point to address is the absence of ST4; this ST appears relatively common in Blastocystis-positive European human patients with diarrhea.…”