Three publications have caught my attention over the past month.
The first one is by my Turkish colleagues Kurt, Dogruman-Al, and Tanyüksel. They just published the paper "Eradication of
Blastocystis in humans: Really necessary for all?" This title implies that treatment of
Blastocystis is recommendable in some cases. The authors appear to acknowledge the view that treatment should be given to symptomatic carriers when all other causes of gastrointestinal symptoms have been rule out, - the popular 'last-resort' approach.
What I think is really useful and admirable is that
the authors leave so many questions open/unanswered, despite the fact that they have been "in business" for so many years, representing some of the most avid Blastocystis researchers. It becomes clear from reading the paper that even in 2016, we still do not know how to eradicate
Blastocystis from the intestine in those cases where we'd really like to try and do so. Importantly, the authors give examples of data supporting the fact that treatment failure may be due to failure of the drug to reach the parasite as well as treatment resistance. They also highlight the possibility that eradication of
Blastocystis by antibiotic/anti-protozoal agents may be due to microbiota perturbation rather than a direct action on
Blastocystis. I also very much appreciate the fact that the authors are embracing the necessity of studying
Blastocystis in a parasite-microbiota-host context in order to be able to draw useful conclusions on its role in human health and disease.
Das and colleagues just published data on
Blastocystis and subtypes of
Blastocystis in IBS patients and controls in New Delhi, India. Using multiple traditional and DNA-based methods, they found that in their study material, the prevalence of
Blastocystis was higher among patients with IBS than among healthy controls. It is not exactly clear how the controls were picked and what type of study population they represented. What I found really useful is the fact that they not only carried out subtyping of
Blastocystis, but also identified subtype alleles. The subtypes and alleles found in the study were very similar to those found recently by Pandey et al. (2015) in Maharashtra, India. Interestingly, it appears that only two subtypes are found in humans in India, namely ST1 and ST3. However, only two studies from India are available on subtypes in humans, to my knowledge, and so we need much more data to draw conclusions.
The last paper that I'm going to address is one by Zanzani and colleagues. When I read the abstract I almost dislocated my lower jaw from stupefaction: Studying the gastrointestinal parasitic fauna of captive non-human primates (
Macaca fascicularis), they found a variety of protozoa and helminths, which is not surprising at all. Neither is it surprising that most macaques were positive for
Blastocystis. Now, what really made my jaw drop was the fact their data on the subtypes found in the macaques challenged the host specificity of
Blastocystis identified so far: They reported finding ST1, ST2, ST3, ST5, and ST7. And so, I had a closer look at the methods used to obtain data on subtypes. I take the liberty of questioning the data, since the authors report using a set of primers for amplification of
Blastocystis DNA targeting the SSU rRNA gene, while using the STS primers developed by Yoshikawa et al. as sequencing primers! I guess that it is possible that the description of the methods was flawed (should have been picked up by the reviewer though), in which case I hope that an erratum will be developed and published.
References:
Das R, Khalil S, Mirdha BR, Makharia GK, Dattagupta S, & Chaudhry R (2016). Molecular Characterization and Subtyping of Blastocystis Species in Irritable Bowel Syndrome Patients from North India. PloS One, 11 (1) PMID: 26784888
