This Month in Blastocystis Research (SEP 2014)

Before leaving for Venice and Padova to introduce Blastocystis to the XXX National Congress of The Italian Society of Protistology (ONLUS), allow me to kick in just a few words for the September issue of 'This Month in Blastocystis Research'.

I will highlight two papers.

The first is a study from the US (Yes, - US data! How rare is that?). The team investigated the prevalence and subtype distribution of Blastocystis among client-owned and shelter-resident cats and dogs. Studies of Blastocystis in companion animals are actually quite rare. The authors used nested PCR for detection, followed by sequencing of PCR products. Interestingly, Blastocystis was not detected in any of the >100 fecal samples from client-owned animals. By comparison, Blastocystis was detected in 10/103 (9.7%) shelter-resident canines, and 12/103 (11.65%) shelter-resident felines. There was no significant difference in Blastocystis spp. carriage rates between the shelter-resident dogs and cats. It is likely that differences in diet and other types of exposure account for Blastocystis being found in shelter-resident animals and not in domestic animals. As for cats and dogs, we don't really know much about what to expect subtype-wise. These animals harboured ST10 mostly, a subtype that has only been found in artiodactyls, NHPs, and lemurs, so far, and - taking these new data into account - with little apparent host preference.

Viktor - an avid fox hunter (in 2007).

Other subtypes included ST1 and one case of ST3, and one case of what was most likely a new subtype - maybe! But then, few animals were positive, and given the different data on subtypes in cats and dogs, it's much too early to speculate on host specific subtypes... for now, it appears that there are none, and that maybe cats and dogs are not really natural hosts? A study by Wang and colleagues identified a plethora of subtypes in dogs: Among 22 positive dogs, most of which were from India, ST1, ST2, ST4, ST5, and ST6 were found. Again, nested PCR was used, and I might have a slight concern that this type of PCR approach is so sensitive that it will pick up the smallest quantity of Blastocystis, maybe even dead Blastocystis or other stages of Blastocystis not necessarily colonising the host (contamination, etc.). But I don't know. The authors of the US study noted that Blastocystis was unlikely to be associated with disease of the animals and were unable to establish a reservoir for human colonisation/infection in these animals.

I never got around to checking Viktor (our cat, pictured above) for Blastocystis. Now it's too late.

I would like to move on to another study. This time the data is from a paper that has just appeared in press in Clinical Gastroenterology and Hepatology. We  analysed faecal DNAs from patients diagnosed with irritable bowel syndrome and healthy individuals. The reason for doing this was due to the fact that intestinal parasite have been speculated to play a role in the development of IBS, a disease affecting about 16% of the adult Danish population. And so we thought that the prevalence of common parasites such as Blastocystis and Dientamoeba fragilis might be higher in IBS patients than in healthy individuals. The study was led by Dr Laura R Krogsgaard, who took a quite unusual approach to collecting questionnaires and faecal samples, namely by collaborating with the company YouGov Zapera.  
We obtained faecal samples from 483 individuals, of whom 186 were cases – ie. patients with IBS – and 297 were healthy controls. DNA was extracted directly from the stool using the easyMag protocol, and the faecal DNAs were submitted to real-time PCR based screening for Blastocystis, Dientamoeba, Entamoeba histolytica and E. dispar, Cryptosporidium, and Giardia.

Above you see the results of the various analyses. Blue columns represent healthy individuals, and orange columns represent IBS patients. Fifty percent of the healthy controls were positive for one or more parasites, while this proportion was significantly lower in IBS patients, 36%. Also for each individual parasite, the number of positive cases was higher among controls than among patients with IBS. Dientamoeba was the most common parasite among healthy controls and IBS patients. In terms of Blastocystis subtypes, the distribution of subtypes between the two groups was non-significant (data not shown).We ended up by concluding that our findings indicated that these parasites are not likely to play a direct role in the pathogenesis of IBS. Longitudinal studies are required to understand their role in gastrointestinal health. 

Still, the role of Blastocystis in human health and disease remains ambiguous, although lots of interesting data is emerging. In order to try and understand the theories behind Blastocystis' potential able to generate disease, I would like to point the readers' attention to a new review, developed by Ivan Wawrzyniak and his prolific colleauges.

Ciao!

References

Krogsgaard LR, Engsbro AL, Stensvold CR, Vedel Nielsen H, & Bytzer P (2014). The Prevalence of Intestinal Parasites is not Greater Among Individuals with IBS: a Population-Based Case-Control Study. Clinical Gastroenterology and Hepatology : the official clinical practice journal of the American Gastroenterological Association PMID: 25229421

Krogsgaard LR, Engsbro AL, & Bytzer P (2013). The epidemiology of irritable bowel syndrome in Denmark. A population-based survey in adults ≤50 years of age. Scandinavian Journal of Gastroenterology, 48 (5), 523-9 PMID: 23506174

Ruaux CG, & Stang BV (2014). Prevalence of Blastocystis in Shelter-Resident and Client-Owned Companion Animals in the US Pacific Northwest. PloS One, 9 (9) PMID: 25226285  

Wang W, Cuttell L, Bielefeldt-Ohmann H, Inpankaew T, Owen H, & Traub RJ (2013). Diversity of Blastocystis subtypes in dogs in different geographical settings. Parasites & Vectors, 6 PMID: 23883734

Wawrzyniak I, Poirier P, Viscogliosi E, Dionigia M, Texier C, Delbac F, & Alaoui HE (2013). Blastocystis, an unrecognized parasite: an overview of pathogenesis and diagnosis. Therapeutic Advances in Infectious Disease, 1 (5), 167-78 PMID: 25165551 

This Month in Blastocystis Research (AUG 2014)

Some August highlights in Blastocystis research:

1) The PRE-IOPCA Molecular Parasitology Workshop took place from the 7-10 August at CINVESTAV, Mexico City. Top-motivated students from some 10-15 countries worked hard from 7 am to 7 pm in dry+wet lab sessions, and we all had a really great time, thanks to both participants and fantastic organisers. There was a 4 h session on Blastocystis molecular epidemiology, and I was pleased to learn that some of the participants currently work with (or plan to work with) Blastocystis. I look forward to doing something similar in Ankara, Turkey on the 27th of May next year (www.blastomeeting2015.com - did you bookmark it?).

Most of the task force of the Molecular Parasitology Workshop (ICOPA 2014).

2) At the actual ICOPA conference, I chaired a session on Blastocystis in the context of IBS, with talks delivered by Ken Boorom, Pablo Maravilla, Pauline Scanlan and myself. In the audience I was honoured to see and meet Dr Hisao Yoshikawa, who has been a main contributor to Blastocystis research over the past 25 years or so (you can look up the publications by Dr Yoshikawa here). Considering the focus of this post, I guess that Pauline's talk was of particular interest, since she presented the data that we just published in FEMS Microbiology and Ecology:

3) The microbial eukaryote Blastocystis is a prevalent and diverse member of the healthy human gut microbiota. That's the title of the paper appearing in FEMS Microbiology and Ecology. The study, led by Pauline, showed that Blastocystis was present in 56% of 105 healthy adults, which is much higher than previously reported from an industrialised county (Ireland). Moreover, a diversity of different subtypes (species) were detected and Blastocystis was present in a subset of individuals sampled over a period of time between six and ten years, indicating that it is capable of long-term host colonisation. These observations show that Blastocystis is a common and diverse member of the healthy gut microbiota, thereby extending our knowledge of the microbial ecology of the healthy human intestine. And one of the interesting things here is: Why do we see this great divide? Why does half of the population appear colonised while the other half not? What are the factors driving successful Blastocystis colonisation? Would some people be refractory to colonisation or does it really boil down to some sort of enterotype-driven phenomenon as previously indicated?

4) I would like to reiterate the paper by Klimes et al. published a study in Genome Biology and Evolution (GBE) on a striking finding in the Blastocystis nuclear genome. Stop codons created by mRNA polyadenylation have been seen so far in mitochondrial genomes only and not in nuclear genomes; however, the authors observered this feature in Blastocystis's nuclear genome. Partly due to limitations of currently available annotation software, this finding ostensibly calls for reannotation of the genome currently available in GenBank (ST7). The paper was highlighted in a separate article in GBE that can be accessed from here.

5) Speaking of Blastocystis genomes: The genome of Blastocystis ST4 (WR1 strain) is now available on-line and can be accessed here.

6) Wang and colleagues studied the location and pathogenic potential of Blastocystis in the porcine intestine. They studied a total of 28 pigs from a commercial piggery, a small animal farm, and a research facility, and all pigs were positive (for ST5, and mixed subtypes were also seen in some). Post-mortem analyses showed that all pigs were consistently found to harbour Blastocystis in the colon, and approximately 90% of the caeca and rectums examined were positive. Some of the pigs were immunosuppresed (Dexamethasone), and interestingly, Blastocystis was occasionally detected in the small intestine, notably in immunosuppressed pigs, suggesting that immunosuprression may alter host-agent relations and predispose to small intestinal colonisation. Histopathological analysis saw the presence of vacuolar and granular forms of Blastocystis, but there was no evidence of attachment or invasion of the intestinal epithelium. The lack of pathology, including inflammation, epithelial damage, mucosal sloughing, and lamina propria oedema, confirmed the trend from a previous study carried out by Ron Fayer's group (see reference below). The study adds to the string of papers finding no evidence in support for Blastocystis causing primary intestinal damage.

6) Lastly, I want to extend a cordial thank you to Shashiraja Padukone and Subhash Chandra Parija, Department of Microbiology, Jipmer, Puducherry, India, for writing up a review of my 'Thoughts on Blastocystis' available on Amazon for the price of only one US$ or so. The review was published recently in Tropical Parasitology and can be accessed here.

And, for those who are worried about researchers 'overselling' microbiome research, there is a small comment in Nature calling for sound scepticism to be applied to research dealing with the relationship between the microbiome and different types of diseases. There is much to be agreed upon, and what I find particularly important, is to take the reductionist approach where possible - in terms of Blastocystis there are lots of ways to study the impact of Blastocystis on bacteria in vitro, and also host microbiota, physiology and immunology in vivo; ways that can be controlled quite diligently. Also, I think that simple validation of methods applied to map e.g. intestinal microbiota is key. This is for some reason something that is generally being utterly and completely ignored. Why?

References 

Fayer R, Elsasser T, Gould R, Solano G, Urban J Jr, & Santin M (2014). Blastocystis tropism in the pig intestine. Parasitology Research, 113 (4), 1465-72 PMID: 24535732

Hanage, W. (2014). Microbiology: Microbiome science needs a healthy dose of scepticism Nature, 512 (7514), 247-248 DOI: 10.1038/512247a

Klimeš V, Gentekaki E, Roger AJ, & Eliáš M (2014). A large number of nuclear genes in the human parasite blastocystis require mRNA polyadenylation to create functional termination codons. Genome Biology and Evolution, 6 (8), 1956-61 PMID: 25015079

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 PMID: 25077936 

Venton, D. (2014). Highlight: Not Like a Textbook--Nuclear Genes in Blastocystis Use mRNA Polyadenylation for Stop Codons Genome Biology and Evolution, 6 (8), 1962-1963 DOI: 10.1093/gbe/evu167

Wang W, Bielefeldt-Ohmann H, Traub RJ, Cuttell L, & Owen H (2014). Location and pathogenic potential of Blastocystis in the porcine intestine. PloS One, 9 (8) PMID: 25093578 

Launch of Official Website for 1st International Blastocystis Symposium.

We are now able to introduce the official website for The 1st International Blastocystis Symposium in May 2015, in Ankara, Turkey. Please check it out!

www.blastomeeting2015.com 

Blastocystis in ICOPA2014

The PRE-ICOPA Workshop on Molecular Parasitology that will take place at CINVESTAV, Mexico City, is only one week away! You can download the program here. There will be sessions on local databases, genomes resources, qPCR, High Resolution Melting Curve Analysis, transcriptomics, proteomics and more, using Toxoplasma, Giardia, Leishmania, Trypanosoma and Blastocystis as model organisms.

I will be heading the 4 h session on molecular epidemiology of Blastocystis, including a 2 h dry lab session allowing students to explore the database at www.pubmlst.org/blastocystis and get familiar with sequence assembly and basic phylogenetic analysis of complete ribosomal genes.

ICOPA 2014 will take place in Mexico City, once known as Tenochtitlán (Work by Wolfgang Sauber; source)

Blastocystis is also on the agenda in one of the ICOPA symposia: On the 11th of August, there will be a late afternoon session on Blastocystis in the context of irritable bowel syndrome (IBS). Speakers will include Dr Pauline Scanlan (IRE), Dr Pablo Maravilla (MEX), Mr Ken Boorom (US), and myself. Incidentally, Dr Scanlan + colleagues just published a paper on Blastocystis in healthy individuals in FEMS Microbiology and Ecology, - you can access the paper - or at least the abstract - here.

See you in Mexico?

This Month In Blastocystis Research (JUL 2014)

For Spanish-speaking Blastocystis geeks, this summer must have been a real treat: Londoño-Franco and colleagues published a paper in Biomédica on Blastocystis in children and Colombia. But not only did they look for Blastocystis in faecal samples, they also sampled from finger nails, house floors, toys, tap water,  vegetables, other food items, etc... It is extremely rare to see studies aiming to identify sources of potential transmission, and I thought that this study would merit a blog post (unfortunately, I will have to rely on the Google translated version with all its potential limitations; I excuse for any misunderstandings).

Of course one of the big questions still remaining in Blastocystis research is: From where do we get this parasite? With more than one billion people colonised on the globe, the transmission pressure must be massive, and it's tempting to expect infectious cysts (or other stages) being more or less ubiquitous. There is some evidence accumulating that the parasite can be water-borne, and we also know that zoonotic transmission can occur (although relatively rarely, supposedly). However, this study takes things way further:

The authors carried out their study in Calarcá where they identified a prevalence of Blastocystis (based on microscopy of stool concentrates) of 57.5% in 275 children less than 5 years old; children aged 48 months or more were more prone to be positive than those who were younger. This is something we see a lot, and it either suggests a cumulative effect of colonisation (once established, colonisation is chronic), or that the behaviour (~exposure) or intestinal microbiota of older children favours colonisation.

Agua de panela (source).

Blastocystis was also found in dogs (63.3%), cats (56.3%), and poultry (35.7%). Moreover, it was found in tap water (38.5%), on toys (29.9%), baby bottles (18.5%), and under the nails of infected children (42.2%), their siblings (44.8%), and their mothers (34.2%). Among the vegetables that are typically consumed raw, it was found most frequently in lettuce (66.7%), and, in descending order, in tomato (44.4%), carrots (37.5%), cabbage (28.6%) and onion (25%). A high occurrence was seen in containers used to store 'aqua de panela', which is allegedly some kind of sugar water (haven't had the opportunity to sample it myself), with 47.7% of the samples positive. I believe that this drink is used as a sweetener and possibly also as a refreshment/energy drink, and maybe served with for instance cheese (image). Taken into account that Blastocystis is not exactly fussy about growth medium requirements, it may not be surprising at all to learn that this type of drink serves as a perfect stronghold for Blastocystis. 

The authors also explored a number of other things, among them i) the relative occurrence of cysts and vacuolar stages in the different types of samples and ii) whether any symptoms experienced over the past month could be attributed to Blastocystis, and iii) risk factors for colonisation. However, Google translate plays tricks on me on some of these bits, so I won't try to go more into detail with these findings. Suffice to say that the approach of distinguishing between different stages should help researchers find out more about which stage(s) that is/are responsible for transmission. Also, if for instance vacuolar stages are found in agua de panela and not cysts, then this might indicate that Blastocystis is actually growing in the drink? Which again is interesting because this would mean that Blastocystis capable of infecting humans can grow at temperatures lower than 37 degrees C.

Now, I could only have great confidence in the diagnostic work carried out by this team; however, I would have absolutely loved molecular confirmation of all of these findings. Also, maybe it would have been an idea to try and culture some of the Blastocystis found on fomites and in food/water to test for viability, or, as mentioned by the authors themselves, to test for viability using trypan blue. However, the authors should be praised for their perseverance and ingenuity, and I hope that this study will inspire other colleagues to pursue and expand on these initiatives and ideas.

This month saw a number of different Blastocystis-related papers, among them a paper from Klimes et al. on issues with Blastocystis genome annotation and polyadenylation-mediated termination codon creation in nuclear mRNA transcripts. Moreover, there's a paper on population structure analysis of seven eukaryotic microbial lineages, including Blastocystis, that apparently makes it possible to infer variable impacts of genetic exchange in populations of predominantly clonal micro-pathogens  (in fact the authors used our MLST data for ST3 in their analyses!). Finally, our colleagues in České Budějovice have produced an interesting review on self-infections with parasites; in the paper they point to the traditional focus on sussing out the pathogenic potential of parasites instead of trying to identify the potentially positive effects of parasite colonisation. Definitely worth a read!

Reference:

Londoño-Franco AL, Loaiza-Herrera J, Lora-Suárez FM, & Gómez-Marín JE (2014). [Blastocystis sp. frequency and sources among children from 0 to 5 years of age attending public day care centers in Calarcá, Colombia]. Biomedica : Revista del Instituto Nacional de Salud, 34 (2), 218-27 PMID: 24967927 

Klimeš V, Gentekaki E, Roger AJ, & Eliáš M (2014). A large number of nuclear genes in the human parasite Blastocystis require mRNA polyadenylation to create functional termination codons. Genome Biology and Evolution PMID: 25015079 

Lukeš J, Kuchta R, Scholz T, & Pomajbíková K (2014). (Self-) infections with parasites: re-interpretations for the present. Trends in Parasitology PMID: 25033775

Tomasini N, Lauthier JJ, Ayala FJ, Tibayrenc M, & Diosque P (2014). How often do they have sex? A comparative analysis of the population structure of seven eukaryotic microbial pathogens. PLoS One, 9 (7) PMID: 25054834 

This Month in Blastocystis Research (JUN 2014) - IMECs Edition

In June there was a paper out in Frontiers in Microbiology by Laura W Parfrey and co-workers identifying the diversity of intestinal microbial eukaryotic communities (IMECs) in humans and other mammals. It's probably one of the most interesting papers I've read for a long time; maybe because it expands on many of the things I've been blogging about - or at least intended to blog about (!) - over the past two years.

What the team did was to do comprehensive analysis of IMECs in both humans and mammals using broad specificity primers for PCR and next generation sequencing technology-based sequencing of the PCR products. While I'm not in a position to validate the analysis of the data, I'd just want to highlight the importance of the approach. It is very rare to see this type of analysis, despite the fact that it's probably the best currently available approach to studying the ecology, homeostasis and public health significance of IMECs. Some of these euks have probably co-evolved with humans and other animals over thousands and thousands of years and therefore may constitute part of the habitual/commensal flora; and so a current working hypothesis (Hygiene Theory) is that losing IMECs ('defaunation' due to Western life style (excessive hygiene and changes in diet)) may prove detrimental to human health and may be one of the most important reasons why we develop for instance allergies and other autoimmune diseases.

Blastocystis virtually obligate finding in Malawi citizens?

And indeed, what the authors found was that among 23 study individuals residing in agrarian communities in Malawi, Blastocystis and Entamoeba were almost obligate findings (not found in two infants, but apart from that almost a consistent finding), while none of the 13 (somewhat age-matched) study individuals from Boulder, Colorado, were infected with Blastocystis, and only two individuals had Entamoeba coli. I was surprised to read that Dientamoeba was not detected in any of the populations; it appears that there is a strong geographical component to the distribution of this parasite, but as the authors mention, specific tools are needed to confirm the absence.

The funny thing is that although this is not a paper specifically on Blastocystis, it is probably the most interesting surveys on Blastocystis coming from the US and a very valuable Blastocystis. Data on Blastocystis in this country is really scarce, but if the prevalence of the parasite is really as low as indicated in this study, then it's maybe quite understandable! And maybe (and this is a highly presumptuous 'maybe', I know) Blastocystis might even therefore an emerging pathogen in the US? When was the US experiencing the great IMECs wipe out? Can it be confirmed? Is there - within the US - also a strong geographical compoenent to the prevalence of IMECs?

Anyway, there are many interesting observations in the paper - and please visit the supporting files. Blastocystis ST11 was confirmed in an elephant (which also hosted Entamoeba moshkovskii! Probably first report of this parasite in an animal). ST13 was found in a Gazelle; not surprisingly, but nice to see independent data confirming what few researchers have found until now. ST4 was found in a sheep and in Okapis; when it comes to ST4, I'm hardly surprised about anything; it appears to be such a sporadic finding in a diversity of non-human hosts (i.e. low host specificity and incidental); one sheep also had ST8, a subtype almost exclusively seen in non-human primates (even South American monkeys rather than for instance African monkeys and apes), so this was surprising too. ST8 was moreover found in two kangaroos (not the first time), in an okapi (different from two first ones) which also hosted ST12, and in an armadillo!

Take home messages include:

1) The study is one of the first to virtually survey IMECs in human and non-human faecal samples using NGS tools.
2) The study confirms a very high prevalence of Blastocystis in some sub-Saharan African communities (for more on this, see a previous blog post), and interestingly, the prevalence and co-infection rate of (up to four species of) Entamoeba was comparably high.
3) Data suggest that IMECs in Western populations are highly reduced compared to rural African populations, but we still need to know more about the relative distribution of for instance fungi and whether these fungi are actually colonising the gut or just carry over from ingested food; right now, it seems as if there might be an inverse relationship between fungal and non-fungal IMECs... something that we can hopefully soon gather sufficient data on for publishing.
4) For those interested in Blastocystis subtype data, including host specificity and geographical distribution, there is a lot to look at in the paper (including supplementary files).

There's a lot more to be said about this paper, but I will sort of leave it here. But please go and read it!

Reference:

Parfrey, L., Walters, W., Lauber, C., Clemente, J., Berg-Lyons, D., Teiling, C., Kodira, C., Mohiuddin, M., Brunelle, J., Driscoll, M., Fierer, N., Gilbert, J., & Knight, R. (2014). Communities of microbial eukaryotes in the mammalian gut within the context of environmental eukaryotic diversity Frontiers in Microbiology, 5 DOI: 10.3389/fmicb.2014.00298

More Details on The 1st International Blastocystis Symposium

Over at www.blastomeeting.com we have posted information on the Organising Committee and the Scientific Programme Advisory Committee of the 1st International Blastocystis Meeting - by some nicknamed the 1st IBS (not too sure about whether this is a fitting acronym, but anyway...).

We will soon be back with more information about the venue, registration, scientific topics, and abstract submission.

Moreover, it is very likely that there will be a pre-symposium workshop on the 27th of May (the day before the conference) on diagnostic methods and tools for studying the molecular epidemiology of Blastocystis. So stay tuned here and at www.blastomeeting.com!

Thanks.

This Month in Blastocystis Research (MAY 2014)

To me, this month was mostly about Blastocystis finding its way to the ASM 2014 general meeting. It was a huge honour for me to be one of the speakers in the Parasitology session 'Passion for Parasites', thanks to an invitation from Dr Lynne Garcia and ASM.

ASM2014 took place in Boston Convention and Exhibition Center.

It's pleasing that the Blastocystis research community is continuously expanding. I currently have contact to several research groups who are venturing into Blastocystis research, including epidemiology, genome sequence analysis, and Blastocystis (and other intestinal microbial eukaryotes (IMEs)) as part of the human intestinal microbiome. At the ICOPA2014 conference in Mexico in August, there will be a full session on Blastocystis from an IBS perspective with talks by Dr Pablo Maravilla, Kenneth Boorom, Dr Pauline D Scanlan and myself. There will also be a pre-congress workshop on molecular parasitology which will include Blastocystis subtyping arranged by Dr Juan David Ramirez Gonzalez and myself.

This month we also launched the website for the 1st International Blastocystis Symposium, which can be accessed at www.blastomeeting.com  - we hope that the meeting will receive great interest and contribute to promoting research on Blastocystis and other IMEs. Please go to the site to sign up for updates.

Moving on to 'paper of the month', I would just briefly highlight a study by Wu, Mirza and Tan, who used Caco-2 human colonic cells and different strains of Blastocystis sp. ST4 and ST7 to compare and demonstrate the strains' relative ability to adhere to enterocytes and to disturb cell barrier function. The paper is very interesting for a variety of reasons. For instance it appears that metronidazole resistance may be linked to a fitness cost as indicated by reduced adhesion ability.

But it would be nice to know how the results reflect the in vivo situation: What actually happens in the colon? It may be so that Blastocystis can adhere to enterocytes and even inflict damage as indicated in the paper, but what if Blastocystis is not able to make it anywhere near the enterocytes?

Now, some parasites are intracellular - e.g. Cryptosporidium and microsporidia -, Giardia has a ventral disc by which it can latch on to the intestinal lining; Entamoebas are motile, etc. Blastocystis is neither intracellular, nor is it motile, but can it attach to enterocytes or is it simply being 'kneeded' and passed along with the remaining luminal content by peristalsis? Or is it lodged in the mucus layer perhaps - trapped by chance, or actively making its way to/through it?

In the colon, two mucus layers exist; an inner layer void of bacteria, and an outer layer that serves as a home for some bacteria but that also prevents these bacteria from reaching the inner layer. Hence, the colon inner mucus layer separates the intestinal lining from the trillions of bacteria inhabiting our large intestine and as such has a tremendously important role in limiting bacterial contact with the epithelium and moving bacteria distally. Mucus is produced by our goblet cells and is made up by mucins, highly glycosylated proteins that we cannot degrade. Moreover, these mucins serve as food for commensal bacteria and are highly resistant to protease activity unless destabilised. The mucus layer traps antimicrobial peptides and other immune effectors and hence creates an effective barrier between the mucosal lining and the microbiota.

Some pathogenic bacteria, and also Giardia for instance, have flagella that allow them to move against the flow caused by secreted mucins, towards the intestinal epithelium, - one way of getting past the iron doors of the mucus layer.

Entamoeba histolytica possesses a lectin-like adhesin that enables it to anchor to the inner mucus layer. After actively destabilising the mucus layer, E. histolytica can disrupt the mucus layer by cysteine protease activity and get into contact with enterocytes. By enzyme activity the parasite can cleave MUC2, the major intestinal mucin, and this may be an initial step in a series of events resulting in invasive disease; however, in many cases enzymatic cleavage of MUC2 may be blocked by glycosylation of the cleavage site; this may be one of the explanations why E. histolytica infection may only sometimes proceed to invasive disease.

Recently, Fayer and colleagues observed that in histology sections Blastocystis was seen to adhere to the intestinal epithelium. However, since about 98% of the mucus is water, the mucus layer may vanish completely during histological procedures with important consequences for the interpretation of observations.

I believe that the use of the mucosal simulator of the human intestinal microbial ecosystem (M-SHIME) would be nearly ideal for studying Blastocystis. M-SHIME is an in vitro dynamic gut model that takes advantage of five double-jacketed vessels, respectively simulating the stomach, small intestine and the three colon regions. The model is supplemented with human gut microbiota and mucin-covered microcosms. My colleagues and I have applied for funding in order to use this model to study Blastocystis ecology, but so far, we have not had any luck with the funding agencies.

Genome and transcriptome studies of Blastocystis should also enable us to identify whether this organism has and expresses proteins that facilitate invasion of the mucus layer and adherence to enterocytes and in which way these potential mechanisms may be influenced.



Note to iOS users: You have the option of making a 'Blastocystis Parasite Blog' app! When you're browsing the site on your iPad for instance, simply add the site to your home screen (use the arrow/box icon in the top of the browser), and there you go - you've created an app icon on your desktop!

Literature: 

Hansson GC (2012). Role of mucus layers in gut infection and inflammation. Current Opinion in Microbiology, 15 (1), 57-62 PMID: 22177113

Fayer R, Elsasser T, Gould R, Solano G, Urban J Jr, & Santin M (2014). Blastocystis tropism in the pig intestine. Parasitology Research, 113 (4), 1465-72 PMID: 24535732 

Johansson ME, Sjövall H, & Hansson GC (2013). The gastrointestinal mucus system in health and disease. Nature Reviews  Gastroenterology & Hepatology, 10 (6), 352-61 PMID: 23478383 

Van den Abbeele, P., Roos, S., Eeckhaut, V., MacKenzie, D., Derde, M., Verstraete, W., Marzorati, M., Possemiers, S., Vanhoecke, B., Van Immerseel, F., & Van de Wiele, T. (2012). Incorporating a mucosal environment in a dynamic gut model results in a more representative colonization by lactobacilli Microbial Biotechnology, 5 (1), 106-115 DOI: 10.1111/j.1751-7915.2011.00308.x

Wu Z, Mirza H, & Tan KS (2014). Intra-subtype variation in enteroadhesion accounts for differences in epithelial barrier disruption and is associated with metronidazole resistance in Blastocystis subtype-7. PLoS Neglected Tropical Diseases, 8 (5) PMID: 24851944

Happy World Digestive Health Day!

Today is World Digestive Health Day!

The theme is 'Gut Microbes -  Importance in Health and Disease'.

United European Gastroenterology (UEG), a professional non-profit organisation combining all the leading European societies concerned with digestive diseases, has launched a short video to raise awareness of such diseases:

In 2000, 600 million patients suffered from a gastrointestinal disease. By 2025, this is predicted to double to 1.2 billion (source).

For those interested (and with access!), there is a special issue on 'The Gut Microbiome in Health and Disease' in the journal Gastroenterology, one of the most renown and established journals in the field.

I would also like to bring your attention to the 5th ASM Conference on Beneficial Microbes, September 27-30 in Washington DC. Deadline for submission of abstracts is July 14.

Wishing everyone a nice World Digestive Health Day!

Blastocystis Conference Website Launched!

I have the pleasure of introducing the official website for the 1st International Blastocystis Symposium scheduled for the 28-29 May, 2015, in Ankara, Turkey.

Please go to www.blastomeeting.com to visit and bookmark the page and to subscribe to updates via email or rss.

We'll be back shortly on the site with updates on the scientific committee, the venue, and how to submit abstracts (including deadline).

Please share. Thanks.