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Blastocystis: Taxonomy, biology and virulence - PubMed

Blastocystis: Taxonomy, biology and virulence

Subhash Chandra Parija et al. Trop Parasitol. 2013 Jan.

Abstract

The unicellular protist Blastocystis has long been an unsolved puzzle for taxonomists, microbiologists and clinicians. Over the years, the organism has been bounced on and off the different branches of the tree of life due the possession of unique phenotypic characters intermediary to different organisms. The organism is polymorphic with only few of forms such as vacuolar, granular, amoeboid, and the cyst form being commonly known. However it could exist in other forms much more frequently than the widely known forms which could be missed by the unaware observer. Certain older concepts in the life cycle of Blastocystis although has been proven wrong are still being followed in various textbooks and other trustworthy internet sources. The causal role of Blastocystis in human disease has long been a subject of controversy. It is widely believed that certain subtypes of the organism are virulent. But this is not so as other factors are also involved in the clinical outcome of the infection. In these contexts, this review intends to shed light on the past misconceptions and the recent findings on the taxonomy, biology and the virulence of this organism.

Keywords: Amoeboid form; Blastocystis; avacuolar form; multi-vacuolar form; stramenophile; subtype.

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Conflict of interest statement

Conflict of Interest: None declared

Figures

Figure 1
Figure 1

(a) Vacuolar forms of Blastocystis having a large centrally placed vacuole showing extensive variation in size (arrows), (b) Granular forms with distinct granules filling the central body, (c) Amoeboid form with characteristic pseudopodia, (d) Cyst forms. Note the smaller size and the characteristic refractile cyst wall surrounded by loose irregular outer coat. Bar-10 μm. Reproduced from Kevin S. W. Tan (reference 1) with permission

Figure 2
Figure 2

(a) Cyst forms are excreted in the faeces of infected hosts, (b) Man acquires infection by consumption of food/water contaminated with faeces containing cysts, (c) Excystation occurs in the large intestine to release the vacuolar form. The vacuolar form (c1) can transform into the granular form (c2) or the amoeboid form (c3) and vice versa. The vacuolar form multiplies by binary fission (other modes of reproduction such as plasmotomy and budding can also occur). The vacuolar form undergoes encystation in the lumen of the large intestine to produce the cyst form which is shed in the faeces

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References

    1. Tan KS. New insights on classification, identification, and clinical relevance of Blastocystis spp. Clin Microbiol Rev. 2008;21:639–65. - PMC - PubMed
    1. Stensvold CR, Suresh GK, Tan KS, Thompson RC, Traub RJ, Viscogliosi E, et al. Terminology for Blastocystis subtypes: A consensus. Trends Parasitol. 2007;23:93–6. - PubMed
    1. Scanlan PD. Blastocystis: Past pitfalls and future perspectives. Trends Parasitol. 2012;28:327–34. - PubMed
    1. Zierdt CH. Blastocystis hominis: Past and future. Clin Microbiol Rev. 1991;4:61–79. - PMC - PubMed
    1. Zierdt CH, Rude WS, Bull BS. Protozoan characteristics of Blastocystis hominis. Am J Clin Pathol. 1967;48:495–501. - PubMed