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

Abstract

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.

Gut bacteria influence Blastocystis sp. phenotypes and may trigger pathogenicity

“…Our findings demonstrated that Blastocystis sp.-infected individuals, regardless of symptoms, had decreased alpha diversity and Pielou's evenness. As observed in our recent study, greater amoebic forms and surface fuzzy coat commonly seen in symptomatic isolates [35] suggest a greater interaction with bacteria in these isolates which could contribute to the alteration of microbiota. On the other hand, lower peak cell numbers in the growth profile of symptomatic isolates implicate potential inhibition from accompanying microbiota.…”

Systematic Review and Meta-Analysis: Epidemiology of Human Blastocystis spp. Infection in Malaysia

“…A recent study has demonstrated variation due to the source of isolation in a single subtype. This suggests the influence of the microenvironment on Blastocystis and its infection [ 105 ]. Hence, to understand the dynamics of Blastocystis infection and its association with pathogenesis, it is necessary to include subtype information in all future epidemiological studies.…”