This Month in Blastocystis Research (DEC 2016)

I would like to end the year by briefly highlight three of the most important/interesting papers in Blastocystis research published in 2016 (and not co-authored by me).

The first article that comes to my mind is one by Pauline Scanlan and colleagues, who took to investigating the prevalence of Blastocystis in US households (family units). The reason why I'm mentioning this article is not so much due to its approach; it's much more related to the fact that even when molecular methods are used (i.e., highly sensitive methods), the prevalence in this population was only 7%, and the vast majority of Blastocystis carriers were adults. The prevalence is much lower in this population (Colorado) than in a country such as Denmark. I'm interested in knowing the reason for this difference. Are people in Colorado less exposed or are they less susceptible than people in Denmark? I'm also interested in knowing why there was only one child among the carriers... we see similar trends elsewhere: Blastocystis is a parasite that emerges only in adolescence and adulthood. Meanwhile, we see a lot of Dientamoeba in toddlers and smaller children, with more or less all children being infected at some point - at least in Denmark; here, geographical differences may exist as well. Mixed infection with Blastocystis and Dientamoeba in adults is not uncommon, so it's not that they outcompete each other.

Next up, is the article by Audebert and colleagues who published in the Nature-affiliated Scientific Reports on gut microbiota profiling of Blastocystis-positive and -negative individuals. I already made a small summary of the article in this post.

While we gain valuable insight into gut microbiota structure, we also need to know what these microbes are able to do. We need to know about the interaction with the host and how they influence our metabolism. I hope to see more studies emerging on the metabolic repertoire of Blastocystis and how the parasite may be capable of influencing the diversity and abundance of bacterial, fungal and protist species in the gut. What would also be useful is a drug that selectively targets Blastocystis so that we can be able to selectively eradicate the parasite from its niche in order to see what happens to the surrounding microbiota and - if in vivo - to the host.

The last article is authored by my Turkish colleagues Özgür Kurt, Funda Dogruman-Al, and Mehmet Tanyüksel, who pose the rhetorical question: "Blastocystis eradication - really necessary for all?" in the special issue on Blastocystis in Parasitology International. For some time I have been thinking of developing a reply to the authors as a Letter to the Editor with the title "Blastocystis eradication - really necessary at all?" Nevermind, quite similar to what we did back in 2010, the authors review the effect of various drugs that have been used to try eradicate Blastocystis. Moreover, they acknowledge the fact that Blastocystis is often seen in healthy individuals, and that its role in the development of gut microbiota and host immune responses should be subject to further scrutiny. They even suggest that the role of Blastocystis as a probiotic should be investigated. It's great to see clinicians think along these lines, since this is an important step towards expanding the revolution lately seen in Blastocystis research, exemplified by studies such as that by Audebert et al. mentioned above.

So, wishing you all a Happy New Year and a great 2017, I'd like to finish by encouraging you to stay tuned; soon, I will be posting some very... interesting... neeeeeeewwwws...

References:

Audebert C, Even G, Cian A, Blastocystis Investigation Group., Loywick A, Merlin S, Viscogliosi E, & Chabé M (2016). Colonization with the enteric protozoa Blastocystis is associated with increased diversity of human gut bacterial microbiota. Scientific Reports, 6 PMID: 27147260 

Kurt Ö, Doğruman Al F, & Tanyüksel M (2016). Eradication of Blastocystis in humans: Really necessary for all? Parasitology International, 65 (6 Pt B), 797-801 PMID: 26780545

Scanlan PD, Knight R, Song SJ, Ackermann G, & Cotter PD (2016). Prevalence and genetic diversity of Blastocystis in family units living in the United States. Infection, Genetics and Evolution, 45, 95-97 PMID: 27545648

This Month in Blastocystis Research (NOV 2016)

Oftentimes, I receive emails from colleagues wanting to know how you subtype Blastocystis, how to grow them in culture, and how to freeze down cultures.

I'm very pleased to announce that Dr Graham Clark and I have developed protocols for exactly these activities and published them in Wiley's 'Current Protocols in Microbiology'; please go here for the subtyping protocol and here for the culture and cryopreservation protocols.
These should not only be seen as SOPs but also as a resource that enables standardization within the field.

Unfortunately, we have not yet come up with a protocol on how to axenise Blastocystis cultures, i.e., get rid of metabolically active organisms other than Blastocystis in cultures while keeping Blastocystis alive and multiplying.

We are well aware that many might not have access to these protocols because they haven't subscribed to Wiley Online Library; good news is that reprints will be available on request!


References:

Stensvold CR, & Clark CG (2016). Molecular Identification and Subtype Analysis of Blastocystis. Current Protocols in Microbiology, 43 PMID: 27858971  

Clark CG, & Stensvold CR (2016). Blastocystis: Isolation, Xenic Cultivation, and Cryopreservation. Current Protocols in Microbiology, 43 PMID: 27858970

This Month in Blatstocystis Research (OCT 2016)

A few things to highlight:

I'm very pleased to announce the Special Issue on Blastocystis recently appearing in Parasitology International - go here for the list of contents. The papers included in this issue represent the breadth of the contributions made to the 1st International Blastocystis Symposium, which took place last year in Ankara. A couple of review and opinion articles written by members of the Scientific Committee are accompanied by several articles outlining original research findings that were presented at the symposium. This special issue is particularly useful for younger researchers who wish to familiarise themselves with some of the methods that are currently in use in surveys of Blastocystis.
Readers should not expect to find articles on Blastocystis in a microbiota context; nor should they expect to see data from seminal studies that challenge the view that Blastocystis is a possible pathogen. Nevertheless, there is an interesting opinion paper with the title "Eradication of Blastocystis in humans--really necessary for all?"

Led by Dr Alison Jacob and Dr Graham Clark, London School of Hygiene and Tropical Medicine, our group just published an article on a comparative study of Blastocystis mitochondrial genomes. In general, mitochondrial genomes differ vastly in length, structure, and gene content across organisms, and by studying these genomes it has been possible to develop hypotheses on how these organisms have evolved including the adaptive/non-adaptive processes involved in shaping organismal and genomic complexity. Unlike most anaerobic eukaryotes, Blastocystis does not have true mitochondria but has mitochondrion-related organelles (MROs; also referred to as mitochondrion-like organelles [MLO]) that contain a genome. In the study in question, we sequenced and compared mitochondrial genomes from subtypes 1, 2, 3, 4, 6, 7, 8, and 9. All of them have the same genes in the same order, but two curiosities were noted. One gene, called orf160, as stop codons near the beginning of the coding region in most subtypes. A second gene, coding for ribosomal protein S4, lacks a start codon in some subtypes.
In both cases, these characteristics would normally prevent a gene from being expressed, but because these genes are otherwise conserved and most of the gene is 'intact', it seems likely that the genes are functional. Ribosomal protein S4 is considered an essential component of the ribosome needed for protein synthesis in the organelle. How the genes are expressed to produce functional proteins remains a mystery, - just one more peculiarity of Blastocystis!

In the growing pool of articles exploring relationships between intestinal parasites and gut microbiota, I was pleased to discover an article by Iebba et al. (2016) on "Gut microbiota related to Giardia duodeanlis, Entamoeba spp. and Blastocystis hominis infections in humans from Côte d'Ivoire". In this observational study, the authors used qPCR to detect groups of bacteria that are indicative of dysbiosis vs eubiosis, dysbiosis being a perturbed, imbalanced microbiota and eubiosis being a healthy, balanced gut microbiota. The authors found that individuals with Blastocystis and Entamoeba were characterised by eubiosis, while individuals with Giardia were characterised by dysbiosis. It says that samples (n = 20) were randomly chosen, but even so, the number of samples tested was low, and care should be taken when interpreting the results. The overall approach, however, is interesting, and somewhat resembles the work that we have been doing in our lab (ref). I also recently blogged about another study with a similar aim (go here to view the post).

I would also like to bring your attention to the EMBO Conference "Anaerobic protists: Integrating parasitology with mucosal microbiota and immunology", which will take place in Newcastle upon Tyne, UK in Aug/Sep 2017 (image). I will be there doing my best to deliver a stimulating talk on current knowledge and advances in Blastocystis and Dientamoeba research. You can visit the conference website by folloing this link. 

References:

Dogruman-Al F, Stensvold CR, & Yoshikawa H (2016). Editorial - PAR INT - special issue on Blastocystis. Parasitology international, 65 (6 Pt B) PMID: 27742000

Iebba V, Santangelo F, Totino V, Pantanella F, Monsia A, Di Cristanziano V, Di Cave D, Schippa S, Berrilli F, & D'Alfonso R (2016). Gut microbiota related to Giardia duodenalis, Entamoeba spp. and Blastocystis hominis infections in humans from Côte d'Ivoire. Journal of infection in developing countries, 10 (9), 1035-1041 PMID: 27694739

Jacob AS, Andersen LO, Pavinski Bitar P, Richards VP, Shah S, Stanhope MJ, Stensvold CR, & Clark CG (2016). Blastocystis mitochondrial genomes appear to show multiple independent gains and losses of start and stop codons. Genome biology and evolution PMID: 27811175

Smith DR (2016). The past, present and future of mitochondrial genomics: have we sequenced enough mtDNAs? Briefings in functional genomics, 15 (1), 47-54 PMID: 26117139

This Month In Blastocystis Research (SEP 2016) - 500,000 PW edition

The Blastocystis Parasite Blog has been going on for about 4 years and 3 months or so. Just now,  the number of pageviews passed 500,000!

I want to thank everyone who has browsed my page. I hope that I have been able to contribute to bringing on a couple of topics for debate and stimulate research into Blastocystis - maybe other parasites too. The FB community is quite active in terms of referring to my website, and so I extend a big Thank You to this community also.

I won't be doing a regular post this time - just hope that some of you will take to (re)visiting one or more of the 174 posts I've developed so far.

I know that I am not replying to all the emails I get; please try again... there are times when I don't really get to check my blog email... but every now and then I do, and I might stumble upon your query... I tend not to reply to those that deal exclusively with questions on how to eradicate Blastocystis. If you are curious about this and my personal opinion on it, please look up posts on "treatment" (you can see the labels in the right side bar).

Please also note that this blog has a FB page.

Thank you for stopping by and for contributing to the debate on Blastocystis.

This Month in Blastocystis Research - AUG 2016

Last month, I asked about your thoughts on Blastocystis and age... is age a limiting factor with regard to the susceptibility to infection/colonisation? One of the reasons why I asked is that we and others have noted that Blastocystis becomes more and more common with age... at least until a certain stage in life (adulthood) and at least in certain countries.

Among the answers I got, I'd like to highlight one from Dr Graham Clark, London School of Hygiene and Tropical Medicine, with whom I've had the tremendous privilege of working for more than 10 years. Dr Clark writes:

In my opinion, prevalence is a mixture of three things: exposure, immunity and ‘loss’.

To illustrate the latter, infection with Entamoeba histolytica (and probably other Entamoeba species) can be lost spontaneously with a half-life of 13 months (in one study at least, Blessmann et al. 2003 J Clin Micro). There is no evidence that immunity is involved, just chance. Extrapolating to Blastocystis, I suspect the same is true – loss can occur spontaneously but what the half-life of colonisation is we have no idea and it would be difficult to evaluate without high resolution genotyping (which is what we used in E. histolytica). If you had a population of infected individuals that were followed over time and a high res[olution] typing method you could calculate rates of loss and of new infections, as we did for E. histolytica.

I do not think there is any evidence for immunity to Blastocystis infection, which leaves exposure. If the rate of exposure is greater than the rate of spontaneous loss then you would get an increase in prevalence with age. I suspect (hope!) exposure is higher in children for behavioural reasons than in adults so you will get a levelling out of prevalence with age to a point where the rate of new infection balances the rate of spontaneous loss. If exposure stays high then this plateau may not be reached.

So why are other parasites different? Probably there is immunity leading to clearance of the infection in children.

Certainly, we have quite good data from Ireland indicating that once established, Blastocystis will keep colonising the GI tract for ages (i.e., many years). Regarding loss, I hope that I'll soon be able to refer to some data that we have obtained in a study on experimental animals.

Exposure is obvisouly something to think about - Blastocystis is transmitted by ingesting food/drink contaminated with Blastocystis and/or improper hygiene. The fact remains that studies using molecular methods for detection have identified most children in Sub-Saharan African study populations as being colonised, while in more developed countries, parasites such as Dientamoeba fragilis are more common in toddlers and smaller children; Blastocystis emerges and gains in prevalence only in teenagers and older individuals... roughly speaking.

One aspect of colonisation that I've been very interested in myself, is whether it's each individual's gut microbiota that "decides" whether Blastocystis colonisation/infection establishes upon exposure. We are seeing some data emerging from a couple of labs on this, and maybe next month I'll be able to bring you up to speed in this matter. To my knowledge, there is not a lot of precedence–if any–for such a situation, but the fact that we have seen quite clear differences in gut microbiota patterns between those who have Blastocystis and those who have not, has left me thinking...

If you want to contribute to the discussion, please drop a line. 

References:

Blessmann, J., Ali, I., Ton Nu, P., Dinh, B., Ngo Viet, T., Le Van, A., Clark, C., & Tannich, E. (2003). Longitudinal Study of Intestinal Entamoeba histolytica Infections in Asymptomatic Adult Carriers Journal of Clinical Microbiology, 41 (10), 4745-4750 DOI: 10.1128/JCM.41.10.4745-4750.2003

Scanlan PD, Stensvold CR, Rajilić-Stojanović M, Heilig HG, De Vos WM, O'Toole PW, & Cotter PD (2014). The microbial eukaryote Blastocystis is a prevalent and diverse member of the healthy human gut microbiota. FEMS microbiology ecology, 90 (1), 326-30 PMID: 25077936