Update on the pathogenic potential and treatment options for Blastocystis sp

Abstract

Although Blastocystis is one of the most common enteric parasites, there is still much controversy surrounding the pathogenicity and potential treatment options for this parasite. In this review we look at the evidence supporting Blastocystis as an intestinal pathogen as shown by numerous case studies and several in vivo studies and the evidence against. We describe the chronic nature of some infections and show the role of Blastocystis in immunocompromised patients and the relationship between irritable bowel syndrome and Blastocystis infection. There have been several studies that have suggested that pathogenicity may be subtype related. Metronidazole is the most widely accepted treatment for Blastocystis but several cases of treatment failure and resistance have been described. Other treatment options which have been suggested include paromomycin and trimethroprim- sulfamethoxazole.

Blastocystis Isolate B Exhibits Multiple Modes of Resistance against Antimicrobial Peptide LL-37

“…3 and 5). This could be one of the reasons why most Blastocystis infections are asymptomatic and self-limiting, as reported previously (5,13). On the other hand, ST7-B is relatively resistant to LL-37 and is also rare in terms of being detected in human populations.…”

“…On the other hand, ST7-B is relatively resistant to LL-37 and is also rare in terms of being detected in human populations. This ST is also resistant to a number of drugs, including metronidazole (13,48), and is capable of downregulating the expression of nitric oxide synthase (14), which is an essential element in the innate immune response. Isolates of ST7 have also been found to cause epithelial barrier disruption and have more adhesive properties in cell cultures (49), thereby making this ST potentially more pathogenic than the rest of the STs.…”

“…There are also variations in drug sensitivities (13,14). Some researchers have suggested that symptomatology is dictated by ST identity (15).…”

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

“…As a consequence of the controversial and unresolved role of Blastocystis in human intestinal disease and the increased awareness of the importance of the gut microbiome (and specific components of the gut microbiome) in human health and disease, research into Blastocystis has increased greatly in recent years (Andersen and Stensvold, 2015;Guinane and Cotter, 2013;Roberts et al, 2014;Scanlan, 2012;Scanlan and Stensvold, 2013;Sekirov et al, 2010). Although the application of sensitive molecular PCR based techniques has faciltated a better appreciation of the prevalence of Blastocystis in human populations, there remains a lack of reliable epidemiological data on the prevalence and genetic diversity of Blastocystis from many regions of the world including the United States.…”

Blastocystis in Health and Disease: Are We Moving from a Clinical to a Public Health Perspective?

“…Randomized controlled treatment studies serving to identify any role for Blastocystis in disease, including alleviation of symptoms upon parasite eradication, are practically nonexistent, which is one of the reasons why no known effective strategy exists with regard to eliminating Blastocystis from the intestine (2,3). The pathogenic potential of Blastocystis remains controversial primarily due to the following reasons: (i) asymptomatic colonization is very common; (ii) evidence suggesting Blastocystis-induced pathogenicity has been inferred mainly from in vitro studies (some of which were reviewed in recent publications [4,5]), while pathogenicity remains to be robustly demonstrated in vivo; (iii) in contrast to the above-mentioned protozoa, no striking phenotypic virulence properties, such as the presence of flagella, lectins, or rhoptries, have been identified, and phagocytosis has been described only once (6); (iv) no Blastocystis-associated outbreaks have been verified; (v) only anecdotal evidence exists regarding clinical improvement upon Blastocystis eradication in patients with gastrointestinal symptoms; and (vi) when epidemiological studies are used for inferring hypotheses on the basis of the pathogenic status of enteric microorganisms, distinctions between endemically and intermittently exposed populations are rarely-if ever-made; such distinctions may be critical to understanding differences in symptom development in the event that host immune response plays a significant role in Blastocystis-associated disease.…”