Current Views on the Clinical Relevance of Blastocystis spp.

Abstract

Blastocystis is an enteric protistan parasite of uncertain clinical relevance. Recent studies indicate that the parasite is a species complex and humans are potentially hosts to nine Blastocystis subtypes, most of which are zoonotic. Subtype 3 is the most common in prevalence studies, followed by subtype 1. Laboratory diagnosis is challenging; the currently recommended diagnostic approach is trichrome staining of direct smears coupled with stool culture. Polymerase chain reaction testing from stools or culture is useful for determining Blastocystis subtype information. The controversial pathogenesis of Blastocystis is attributed to subtype variations in virulence; although current studies seem to support this idea, evidence suggests other factors also contribute to the clinical outcome of the infection. Clinical signs and symptoms of blastocystosis include abdominal pain, diarrhea, bloating, and flatulence. Extraintestinal manifestations, predominantly cutaneous, also were reported. In vitro and animal studies shed new light on the pathobiology of Blastocystis.

Prevalence and genetic diversity of Blastocystis in family units living in the United States

“…A renewed research interest in the microbial eukaryote Blastocystis has been largely driven by a greater appreciation of its genetic and phenotypic diversity, ubiquity in human and animal populations, and its potential role in both human health and disease (Andersen and Stensvold, 2015;Tan et al, 2010). Currently, there is little information on…”

“…Secondly, environmental sources such as drinking water may also be a potential source of Blastocystis (Leelayoova et al, 2008;Taamasri et al, 2000). Poor sanitation and unsuitable water treatment resulting in the consumption of contaminated water are likely to be contributory in this regard (Taamasri et al, 2000;Tan et al, 2010). Finally, direct human-to-human transmission through contact with infected individuals (directly or indirectly via contaminated food and water) has also been postulated (Anuar et al, 2013;Yoshikawa et al, 2000).…”

Identification of Blastocystis subtypes in clinical stool samples from Sao Paulo City, Brazil

“…Although, the pathogenic role of Blastocystis sp. is controversial, accumulating evidence from recent studies supports the idea that they constitute an emerging pathogen (Tan, 2008;Tan et al 2010). This enigmatic organism has also been identified in a wide range of animals.…”

Molecular Epidemiology of Blastocystis in Lebanon and Correlation between Subtype 1 and Gastrointestinal Symptoms

“…It may also play a significant role in irritable bowel syndrome (IBS) and has been linked with urticaria. [2][3][4][5][6] According to recent in vivo and in vitro studies as well as genomic data, a model for pathogenesis of this parasite was proposed, and mainly involves cysteine proteases secreted by the parasite. [5][6][7] Blastocystis organisms found in different hosts are morphologically indistinguishable.…”

“…[2][3][4][5][6] According to recent in vivo and in vitro studies as well as genomic data, a model for pathogenesis of this parasite was proposed, and mainly involves cysteine proteases secreted by the parasite. [5][6][7] Blastocystis organisms found in different hosts are morphologically indistinguishable. However, this genus exhibits an extensive genetic diversity and at least 13 subtypes (STs) have been described on the basis of molecular data, [8][9][10] which showed sufficient genetic divergence to be classified as separate species.…”