Distinct Phenotypic Variation of Blastocystis sp. ST3 from Urban and Orang Asli Population-An Influential Consideration during Sample Collection in Surveys.

Abstract

Simple SummaryBlastocystis sp. is a common intestinal protozoan of humans with the phenotypic characteristics strongly associated with its activity, including pathogenicity. This characteristic varies, but the variation has not been clearly understood. The present study evaluates the variation when a single subtype of Blastocystis sp. was isolated from a population with distinct gut microbial composition, namely, the urban and orang asli(indigenous) population. Blastocystis sp. cells isolated from orang asli individuals had a higher growth rate with elevated resistance to harsh conditions. Distinct surface coats with amoebic forms were noticed in parasite cells from urban individuals. Proteases, commonly a virulent factor in other parasites, showed variation depending on the isolation source. Stimulation of cancer cell proliferation by only Blastocystis sp. isolated from urban individuals is suggestive of the variation at the antigenic level. This phenotypic variation suggests that implicating subtype to pathogenicity may be too early, and a deeper understanding of Blastocystis sp. and microenvironment interaction is essential.Blastocystis sp. is a globally distributed protozoan parasite with uncertain pathogenicity. Phenotypic variation in Blastocystis sp. suggests its adaptation; however, the phenotypic features of Blastocystis sp. ST3 from a distinct source of isolation is unknown. Blastocystis sp. isolated from individuals in urban and orang asli (indigenous population in Selangor, Malaysia) settlements were studied for phenotypic characteristics such as growth profile, morphology, ultrastructure, and resistance to harsh conditions. Subsequently, pathogenic potentials, such as in protease activity and the ability to stimulate the proliferation of cancer cells, were assessed. Higher parasite counts with granular and apoptotic forms were found in Blastocystis sp. from orang asli individuals. Cells with fuzzy coats and amoebic structures which seemingly implicate increased interaction with bacteria were seen predominantly in urban symptomatic persons. Also, Blastocystis sp. from orang asli isolates resisted harsh environments, suggesting longer co-adaptation to the hosts. Urban and orang asli symptomatic isolates possessed a predominance of only cysteine protease, whereas all the asymptomatic isolates showed significantly higher cysteine, serine, or aspartic protease activity. However, only solubilized antigen from urban symptomatic isolates showed significant stimulation of cancer cell proliferation. For the first time, our findings demonstrate significant phenotypic variation in a single subtype, ST3 of Blastocystis sp., isolated from urban and orang asli populations that are known to have distinct gut microbial compositions. The outcome emphasizes the importance of identifying people’s locations and lifestyles during sample collection before forming conclusions on the prevailing data and implicating subtypes to pathogenicity. The environment plays a significant role in Blastocystis sp. infection.