Blastocystis Hits The 1,000 Entry Mark In PubMed

Yesterday, the number of Blastocystis entries in PubMed reached 1,000! PubMed is a public resource comprising more than 22 million citations for biomedical literature from MEDLINE, life science journals, and online books.

In comparison, there are currently 7,641 entries on Entamoeba, 6,630 on Cryptosporidium and 235 entries on Dientamoeba.

I plan to introduce the "Hall of Fame in Blastocystis Research" in a future post, but already now I can reveal that the researcher with most Blastocystis-related publications is Dr Hisao Yoshikawa according to Web of Science (WoS), which currently returns 895 hits on a search on Blastocystis; Dr Yoshikawa has at least 43 publications on Blastocystis alone (WoS), and at least 37 Blastocystis-specific peer-reviewed journal articles (PubMed) since 1987.

Blastocystis in Non-Human Primates

If my recent blog post "Blastocystis aux Enfers" could be described as "Blastocystis meets Dante Alighieri", then this post might come across as "Blastocystis meets Sir David Attenborough" (with all due respect to both of these gentlemen!).

Non-human primates (NHPs) include apes (hominoids), Old World monkeys (cercopithecoids), New World Monkeys (ceboids) and prosimians such as lemurs. I have been so fortunate to be involved in a study of Blastocystis in NHPs; a study which was led by Dr Alfellani with several co-investigators, and which has just appeared online in the journal Parasitology (click here to be diverted to the the website - first view article section).

The study is the first of its kind aiming to provide a substantial insight into the host specificity of Blastocystis in NHPs and included subtype observations for 441 captive and free-living animals representing no less than 30 genera; most of the data were generated during the study, while sporadic observations from similar studies were also included.

It was a huge study with a lot of interesting information, and I will try and summarise some of the points here.

Apes such as bonobos, chimps, gorillas and orangutans were colonised by some of the most common subtypes in humans, namely ST1, ST2, and ST3, accounting for about 77% of the cases. Contrary to humans though, ST5 also appeared rather common, accounting for about almost 14% of the cases, and some of the gibbons studied had ST8. Interestingly, a chimp and a gibbon were found to be hosts of a new subtype, ST15.

Old World monkeys were studied to an even larger extent, and again, ST1, ST3 and ST2 predominated, accounting for about 95% of all cases of single subtype infection. Here ST5 was also seen (2%) but only in langurs/lutungs and vervet monkeys. Interestingly, ST8 was seen only in 1/226 cases. ST13 was found by colleagues in Tanzanian colobus monkeys (Petrasova et al., 2011), and 8% of the 226 cases represented mixed/unknown subtype infections.

Woolly monkey (Lagothrix lagotricha) (Source)

New World monkeys included in the study were mainly represented by woolly monkeys, and these were colonised first and foremost by ST8 (49%), but ST3, ST2, ST1 were also found. So was a single case of ST4, which in general appears to be surprisingly rare among NHPs.

A few observations on lemurs were included, and such animals appear to host a vast variety of subtypes with no particular predilection, hence ST1, ST2, ST4, ST8, ST10 and ST15.

Ring-tailed lemur (Lemur catta) (Source).

The most striking differences between humans and NHPs in terms of colonisation by Blastocystis subtypes is that humans are very rarely colonised by ST5, while this subtype appears common in apes and Old World monkeys. ST8 was seen only in arboreal apes and in woolly and howler monkeys, which are also tree-dwellers, and it is tempting to think that ST8 is found mainly in tree-dwelling NHPs; to my knowledge, ST8 has not been found in non-primate hosts, except for once in a bird. Human colonisation by ST8 has been demonstrated only very rarely, for instance in a Danish woman returning from holiday in Indonesia and in animal keepers. Conversely, ST4 is seen extremely rarely in NHPs, while very common in humans in some parts of the world, apparently especially in Europe. These clear discrepancies in subtype distribution in humans and NHPs may boil down to host specificity and/or apparent geographically restricted range of some subtypes.

Another striking observation was that cryptic host specificity exists in ST1 and ST3, meaning that ST1 and ST3 strains found in NHPs overall differ genetically from strains found in humans belonging to the same subtypes, adding support to our previous findings.This suggests that humans are generally colonised by other strains than those found in NHPs. It will be interesting to see, whether other types of hosts sharing these subtypes carry distinct, host-specific strains. While MLST is probably the best way of testing for this, a lot of information can be obtained simply by barcoding. Pets, for instance, may share subtypes seen in humans, and so barcoding of "pet blasto" may be one of the very interesting pathways to knowledge.

We found no evidence of those subtypes that we have nicknamed "avian subtypes", namely ST6 and ST7. In some parts of the world, these two subtypes do not appear uncommon in humans; in Denmark and Sweden, for instance, ST7 is seen on quite a few occasions. But, interestingly, both STs are apparently absent in NHPs.

Langurs - the front cover of one of my favourite books showcasing works by the magnificent Walton Ford.

Incidentally, there is a sequence in GenBank from a gorilla (JX159284) which possibly represents a novel subtype, which is related to reptilian Blastocystis, and so it appears that the host spectrum and diversity of Blastocystis in NHPs continues to unfold.

A recent study saw that faecal microbiomes of wild non-human primates co-vary with host species, hence reflecting host phylogeny. This was evidenced by higher intra-species similarity among wild primate species, which may reflect species specificity of the microbiome in addition to dietary influences. This may in part explain the differences in Blastocystis subtypes seen in different NHP host species, but it is also possible that differences in subtypes reflect differences in habitat (and thereby possibly exposure) or geographical differences in subtype distribution. Indeed Homo sapiens is host to a variety of subtypes, and while ST4 is common in Europe, it appears virtually absent in many other parts of the world. Likewise, the differences in the prevalence of ST8 may reflect differences in geographical distribution, habitat and diet (arboreal vs. ground) as well differences in host specificity.

The overall interesting thing here is the schism of exposure vs. host specificity.


Suggested reading:

Alfellani, M., Jacob, A., Perea, N., Krecek, R., Taner-Mulla, D., Verweij, J., Levecke, B., Tannich, E., Clark, C., & Stensvold, C. (2013). Diversity and distribution of Blastocystis sp. subtypes in non-human primates Parasitology, 1-6 DOI: 10.1017/S0031182013000255

Yildirim S, Yeoman CJ, Sipos M, Torralba M, Wilson BA, Goldberg TL, Stumpf RM, Leigh SR, White BA, & Nelson KE (2010). Characterization of the fecal microbiome from non-human wild primates reveals species specific microbial communities. PloS one, 5 (11) PMID: 21103066

Stensvold CR, Arendrup MC, Nielsen HV, Bada A, & Thorsen S (2008). Symptomatic infection with Blastocystis sp. subtype 8 successfully treated with trimethoprim-sulfamethoxazole. Annals of tropical medicine and parasitology, 102 (3), 271-4 PMID: 18348782

Stensvold CR, Alfellani M, & Clark CG (2012). Levels of genetic diversity vary dramatically between Blastocystis subtypes. Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases, 12 (2), 263-73 PMID: 22116021

Technical issues...

I'm experiencing a problem with my post titles being displayed as uncials (sort of nested in each post with blog text wrapped around it), when using Firefox or Chrome (also the headline link function has been disabled). I'm trying to fix it, but for now, I recommend viewing the blog in Internet Explorer rather than eg. Firefox or Chrome. If anyone knows how to fix this, please give me a shout!

Have a great weekend!

Blastocystis and IBD

We recently published what could be seen as a pilot study on inflammatory bowel disease (IBD) and the two most common intestinal parasites, Blastocystis and Dientamoeba fragilis.

The aim of the study was to identify possible differences in the prevalence of infection with Blastocystis and D. fragilis in patients with active and inactive IBD compared to controls.

We included 100 Danish patients with IBD (42 with Crohn's Disease, 41 with ulcerative colitis and 17 with ileal pouch-anal anastomosis) and 96 controls, used state-of-the-art diagnostics for Blastocystis and D. fragilis (PCR) and we saw striking differences in prevalence. While 19% of all healthy individuals had Blastocystis, only 5% of those with IBD had Blastocystis, and of the 42 patients with Crohn's Disease, only 1 had Blastocystis. In contrast, D. fragilis was not more common in healthy individuals than in IBD patients. Also, in patients with ulcerative colitis, Blastocystis was significantly more common in patients with inactive disease compared to patients with active disease.

Absence of Blastocystis in patients with Crohn's Disease and active ulcerative colitis may be due to unfavourable conditions for colonisation and should be explored further in order to investigate whether these potentially unfavourable conditions reflect differences in the composition of the microbiota in these patients, and/or whether this has something to do with host immunity. We are currently confirming the virtual absence of Blastocystis in Crohn's patients in another study based on metagenomic analysis of faecal DNA, and it will be very interesting to analyse the differences in Blastocystis prevalence in view of potential differences in bacterial communities.

The literature on Blastocystis and IBD is relatively limited, and I plan to return, maybe later this year, with a more elaborate post on the topic.

Reference:

Petersen AM, Stensvold CR, Mirsepasi H, Engberg J, Friis-Møller A, Porsbo LJ, Hammerum AM, Nordgaard-Lassen I, Nielsen HV, & Krogfelt KA (2013). Active ulcerative colitis associated with low prevalence of Blastocystis and Dientamoeba fragilis infection. Scandinavian journal of gastroenterology PMID: 23528075

Happy Birthday!

In these very hours, my daughter is turning two years old! This blog was put up one year ago as she was celebrating the conclusion of her first year on this planet, and given all the fun I've had along the way putting up posts on this and that, I'd like to dedicate the blog to her. In return(!), I take the liberty of using some of her artwork for this post which marks the birthday of the Blastocystis Parasite Blog.

Artwork by Raiya Rochelle Traub

It's surprising to me that this blog has had more than 50,000 views in only one year. Due to all the feedback I get, I'm prone to believe that most of the page views reflect factual "blog consumption" (rather than referral spam and bots). Anyway, even if there were only a few people out there who'd stop by every now and then, my efforts would certainly be worthwhile. 
Blastocystis has been known for more than 100 years. But it is only recently that we have found tools to enable accurate distinction of Blastocystis carriers from non-carriers, thanks to DNA-based diagnostic methods. Last year, we published a paper on our new real-time PCR in Journal of Clinical Microbiology, and it seems as if we now finally have the chance to try and use it for screening a larger panel of faecal DNAs from patients with and without intestinal symptoms to get an idea about the factual prevalence of Blastocystis in this type of samples with the added benefit of analysis of colonisation intensity. It's very exciting...

And to those who are involved in Blastocystis subtyping, -  in case you didn't see it, there is a paper out on the comparison of the two principal methods used for subtyping which you might find useful.
I've also added a few lines on barcoding in "Lab Stuff" for those who are new to subtyping and want to practice a bit - please go here.

We are currently trying to strengthen collaborative efforts of different labs across the world and we are facing some very exciting challenges, involving the generation and analysis of data output related to genomics, transcriptomics, metagenomics and possibly proteomics; more about that in "Season II" of the Blastocystis Parasite Blog!

But for now: Happy birthday, Raiya! And Happy Easter everyone!

Suggested reading:

Stensvold CR (2013). Comparison of sequencing (barcode region) and sequence-tagged-site PCR for Blastocystis subtyping. Journal of Clinical Microbiology, 51 (1), 190-4. PMID: 23115257 

Stensvold, C., Ahmed, U., Andersen, L., & Nielsen, H. (2012). Development and Evaluation of a Genus-Specific, Probe-Based, Internal-Process-Controlled Real-Time PCR Assay for Sensitive and Specific Detection of Blastocystis spp. Journal of Clinical Microbiology, 50 (6), 1847-51. DOI: 10.1128/JCM.00007-12

LUMINEX xMAP Technology in Parasite Diagnostics

Over the past few years nucleic acid based methods have revolutionised parasite diagnostics in modern clinical microbiology (CM) labs. Real-time PCR is really gaining a foothold in CM labs, but despite the opportunity for plexing, mostly only up to 6 DNA targets can be included in each assay (due to the number of available channels).

LUMINEX xMAP technology used for detection of specific nucleic acids (Dunbar, 2006) bypasses this limit, and up to 100 DNA targets can be included in one single assay in a 96-well plate format. You can read about the technology here.

Immunology in the Gut Mucosa

Nice video!

Extremophilic Eukaryotes

My recent post Blastocystis aux Enfers was my "literary take" on biological adaptation of intestinal parasitic protists, using Blastocystis as an example. As a parasitologist you'd come across many peculiar and shrewd biological adaptations and life cycles, and I hope to be able to give some examples in a future post. Actually, there is a parasite which is quite common in humans, maybe even just as common as Blastocystis, which is also single-celled, but which may have a much more complicated life cycle than Blastocystis, namely Dientamoeba fragilis; a colleague of mine is currently doing his PhD on Dientamoeba and he has collected multiple sources of evidence to confirm the hypothesis that this parasite is transmitted by a vector, namely pinworm, probably along the same way that Histomonas meleagridis – the cause of blackhead disease in especially turkeys – is transmitted by heterakids (which again are transmitted by parathenic hosts such as earthworms, which get eaten by turkeys, chickens, etc.). Anyway, I’ll probably get back to Dientamoeba, once his data are out.

Meanwhile, Blastocystis comes out of a very heterogeneous group of organisms called Stramenopiles, many of which are algae. Algae are photosynthetic organisms found in habitats as diverse as glacial ice and hot springs.One of these algae is named Galdieria sulphuraria, which is a remarkable unicellular eukaryote inhabiting hostile environments such as volcanic hot sulfur springs where it is responsible for about 90% of the biomass; indeed this certainly qualifies as "Galdieria aux enfers"!

Blastocystis video

Just saw this on YouTube and had to share it. This is Blastocystis (and other microorganisms) viewed through a microscopy (light microscopy). Note that this is Blastocystis from a chicken, but Blastocystis from humans looks the same; at least I don't know how to tell the difference. I wonder whether this is from a culture or a completely fresh egestion... looks more like a culture to me. Note how the Blastocystis looks almost like fat cells...

The video comes with some nice music as well!

Open Access papers in Nature Reviews on functional dyspepsia

"Functional dyspepsia is one of the most common functional gastrointestinal disorders worldwide. Although the condition does not affect life expectancy, it can have a marked influence on quality of life, and is associated with a high economic burden; an estimated US$1 billion per year is spent on the management of functional dyspepsia in the USA alone. This comprehensive Focus issue from Nature Reviews Gastroenterology & Hepatology contains seven Reviews that have been specially commissioned to cover key themes in functional dyspepsia. Experts from around the world provide up-to-date overviews of the most important topics in the field, including the influence of dietary, lifestyle and psychosocial factors, relevance of Helicobacter pylori infection, overlap with GERD, changes in gastrointestinal tract structure and function, symptom pattern and validity of the Rome III criteria, as well as current and emerging treatment options."

For the bunch of papers, please go here.