Is Blastocystis a pathobiont? Prevalence data and beyond

While a lot of research in gut microbiota is focused on the bacterial community, little research data is available on the microeukaryotic community. Knowledge about the role of the microeukaryotic community in the gut and its interaction with the bacterial community and its host is insufficient (Anderson et al., 2013).

One of the commonly observed microeukaryotes is Blastocystis. There is ongoing debate on whether this microeukaryote is pathogenic or a common resident. While there are reports of potential pathogenic associations of Blastocystis with irritable bowel syndrome (Fouad et al., 2011), the data obtained from numerous epidemiological surveys in many developed, developing and low-income countries has demonstrated Blastocystis to be widely distributed in healthy individuals (Alfellani et al., 2013).

Although sufficient data exist for most of the diverse populations of the world, a study on the diverse, second largest population was [previously] missing. For the first time, prevalence of Blastocystis is now reported in the Indian sub-population. Despite being considered as a developing nation and predicted to have higher prevalence of Blastocystis, the study by Pandey et al., (2015) demonstrated an average prevalence of 27% in adults. The prevalence reported in the Indian sub-population is lower than reports from some of the other developing countries (Alfellani et al., 2013). The study by Pandey et al. (2015) highlights the need for further detailed studies on Blastocystis species in Indian populations (both healthy and in disease conditions such as IBS) to identify whether there are differences between health and disease states, and if so, which genotype is associated with disease.

The prevalence data to date suggests that Blastocystis may represent a potential microeukaryotic pathobiont which is a commensal member but under certain conditions such as inflammation may behave as a pathobiont. However, such a possibility will require further studies that deal with elucidating the mechanistic role of Blastocystis in human health.

References:

Alfellani et al., (2013) Variable geographic distribution of Blastocystis subtypes and its potential implications. Acta Trop.  Apr;126(1):11-8. doi: 10.1016/j.actatropica.2012.12.011.

Andersen et al., (2013) Waiting for the human intestinal Eukaryotome. The ISME Journal (2013) 7, 1253–1255; doi:10.1038/ismej.2013.21

Fouad, M.M. Basyoni, R.A. Fahmy, & M.H. Kobaisi. (2011) The pathogenic role of different Blastocystis hominis genotypes isolated from patients with irritable bowel syndrome. Arab. J. Gastroenterol., 12 (2011), pp. 194–200

Pandey et al., (2015) Prevalence and subtype analysis of Blastocystis in healthy Indian individuals. Infect Genet Evol. Feb 17;31C:296-299. doi: 10.1016/j.meegid.2015.02.012.

Preview image shows four common forms of Blastocystis hominis – vacuolar, granular, amoeboid, and cyst forms.
Image created by Valentia Lim Zhining on May 14th, 2006.
The file is licensed under the Creative Commons Attribution-Share Alike 2.5 Generic license.

Sudarshan Shetty
Sudarshan Shetty
PhD candidate at Wageningen UR, studying the human gut microbiome for understanding its role and function in human health.