Showing posts with label diagnosis. Show all posts
Showing posts with label diagnosis. Show all posts

Friday, April 1, 2016

This Month in Blastocystis Research (MAR 2016)

I'm going to dedicate this post entirely to a recent case presented by my wonderful colleague Bobbi Pritt (Mayo Clinic) in collaboration with Blaine Mathison (CDC), whom I have also been so fortunate to meet.

Please go here to see the case.

Creepy Dreadful Wonderful Parasites: Case of the Week 390.

Let me use the opportunity to congratulate Bobbi Pritt on her fantastic work, admirable skills, and dedication to parasitology!

And by the way; why not treat yourself to Bobbi's 2016 parasite calendar available for purchase here.

Sunday, November 1, 2015

This Month in Blastocystis Research (OCT 2015)

I'm actually going to skip the small review I do each month for a variety of reasons. Instead, I'm just going to upload a presentation I gave in Tilburg, The Netherlands, a bit more than a week ago, before attending the UEG Week in Barcelona.

I uploaded it to Google Drive, hoping that it will be easy to download for everyone interested. I have not included any notes, hoping that the slides will be pretty much self-explanatory.

I think there is even a bit of Danish in there, - hope you don't mind! Also, the preview option does not work very well, so make sure you download it.

If the presentation left you wondering a bit and wish for more, why not look up my publications listed in PubMed? They are available here.  Some of them can be downloaded for free.

Thank you for your attention.

Monday, October 5, 2015

This Month in Blastocystis Research (SEP 2015)

The month of September saw the publication of the first data on Blastocystis subtypes going out from Qatar. Abu-Madi and colleagues--who have already been quite prolific in terms of surveying intestinal parasitic infections in Qatar--studied the positive rate of Blastocystis in 608 apparently healthy subjects arriving in Qatar for the first time, identifying a prevalence of 71% as identified by PCR. Strikingly, the positive rate by microscopy of the corresponding samples was only 7%. Three subtypes were idenfied, with ST3 being the most common subtype, followed in prevalence by ST1 and ST2. The study is important for at least two reasons: It confirms the drawback of basing Blastocystis epidemiological research on data generated using microscopy alone, and it confirms the virtual absence of ST4 outside of Europe.

Increased sensitivity of PCR relative to microscopy was also confirmed in a study carried out in Malaysia (I presume) by Ragavan and colleagues. This group surveyed the Blastocystis positivity rate among IBS and non-IBS patients analyzing colonic aspirates, including a total of 109 individuals. Given the data available on Blastocystis prevalence, I was quite surprised to learn that this group failed to detect Blastocystis in any of the samples by microscopy and culture. Using PCR (the subtype-specific [STS] primers were used as diagnostic primers), the group identified Blastocystis in 6 IBS patients and 4 non-IBS patients. Also these figures appear quite low. However, there is very little information available on the non-IBS patients, and since all study individuals were subject to colonscopy, this group of individuals might be suffering chronic and potentially severe intestinal disease, including for instance colorectal cancer, inflammatory bowel disease, etc., which would explain the low prevalence of Blastocystis observed among these individuals. Indeed, evidence is accumulating that the more "gut healthy" you are, the larger the probability of being Blastocystis-positive. I noticed that the colonic aspirates were spun down using 3,000 rpm prior to culture and microscopy; this process might have had an impact on cell viability and morphology; still, DNA should be detectable following this process. Meanwhile, we recently showed (Scanlan et al., 2015) that the sensitivity of the STS primers is relatively low, which is why the use of real-time PCR is recommendable for PCR-based screening. To see an example of how the STS primers perform relative to barcoding primers, go here (Suppl Table 2).
Moreover, care should be taken when reading this paper, since I'm fairly convinced that the subtype terminology used in the study is different from the consensus terminology (Stensvold et al., 2007). It says that the subtypes detected included ST2, ST3, ST4, and ST5; if this reflects the terminology that went along with the original description of the STS primers, these subtypes correspond to ST7, ST3, ST6, and ST2, which to me would be a more likely subtype distribution, taking this particular region into consideration, and given the fact that ST5 appears to be extremely rare in humans. 

It's always interesting to expand on the natural host spectrum of Blastocystis. The parasite has been found in a perplexing array of hosts, but some host specificity has been observed. When it comes to animals held by humans as livestock or pets, we know that pigs and cattle are commonly, if not consistently, colonised by Blastocystis with some quite specific subtypes. With regard to pets, dogs and cats have been found positive, but there seems to be increasing evidence that these animals are not natural hosts (see also Wang et al., 2013). Osman and colleagues, recently published a survey on Cryptosporidium and Blastocystis in dogs using sensitive molecular methods, demonstrating a prevalence of Blastocystis of only about 3%. Moreover, the subtypes 2 and 10 were found, and ST10 is found mostly in cattle, and never before in dogs, as far as I know, which could suggest accidental colonisation - and possibly not a very long-lasting one. Similarly, when humans are found to be colonised with subtypes rarely found in humans, such as ST6, ST7, and ST8, it would be interesting to know for how long these subtypes are capable of "staying put" in the human intestine.


Abu-Madi M, Aly M, Behnke JM, Clark CG, & Balkhy H (2015). The distribution of Blastocystis subtypes in isolates from Qatar. Parasites & Vectors, 8 PMID: 26384209

Osman M, Bories J, El Safadi D, Poirel MT, Gantois N, Benamrouz-Vanneste S, Delhaes L, Hugonnard M, Certad G, Zenner L, & Viscogliosi E (2015). Prevalence and genetic diversity of the intestinal parasites Blastocystis sp. and Cryptosporidium spp. in household dogs in France and evaluation of zoonotic transmission risk. Veterinary Parasitology PMID: 26395822   

Ragavan, N., Kumar, S., Chye, T., Mahadeva, S., & Shiaw-Hooi, H. (2015). Blastocystis sp. in Irritable Bowel Syndrome (IBS) - Detection in Stool Aspirates during Colonoscopy PLOS ONE, 10 (9) DOI: 10.1371/journal.pone.0121173  

Scanlan PD, Stensvold CR, & Cotter PD (2015). Development and Application of a Blastocystis Subtype-Specific PCR Assay Reveals that Mixed-Subtype Infections Are Common in a Healthy Human Population. Applied and Environmental Microbiology, 81 (12), 4071-6 PMID: 25841010   

Stensvold CR, Suresh GK, Tan KS, Thompson RC, Traub RJ, Viscogliosi E, Yoshikawa H, & Clark CG (2007). Terminology for Blastocystis subtypes--a consensus. Trends in Parasitology, 23 (3), 93-6 PMID: 17241816

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

Saturday, February 28, 2015

This Month in Blastocystis Research (FEB 2015)

Before heading off to visit dear colleagues at the Public Health Agency of Sweden tomorrow morning, I thought I'd do a quick 'This Month...' post.

Tropical Parasitology has published a paper by Elghareeb and colleagues on  'Laboratory Diagnosis of Blastocystis in Diarrheic Patients'. I was asked to do a Guest Commentary on their paper, and if your're interested you can download my comments here for free (html version). The paper by Elghareeb et al. should also be free for download at the website.

I have been very lucky to work together with Dr Prashant K Pandey and his colleauges in Pune, India. Together we just published the first data on Blastocystis subtypes ever to appear in India for what I know. We subtyped Blastocystis in a cohort of healthy Indian individuals, and found ST1 and ST3 in 27/100 adult individuals tested, while other common subtypes, ST2 and ST4, were absent. Remarkably, ST3 was seen in all positive individuals, while ST1 was seen only in mixed infections. The strains (alleles) found in India were no different to those found in for instance Europe.

There is a paper out by Rossen and colleagues from The Netherlands showing that Blastocystis is relatively uncommon in patients with active ulcerative colitis (UC) and significantly less common in UC patients (13.3%) than in healthy individuals (32.5%). This is completely in line with data that we generated in Denmark a couple of years ago. In fact, at two separate occasions we have been able to look into patients with inflammatory bowel disease. In both cases (one study has been submitted for publication), hardly any Blastocystis was found in patients with Crohn's disease, while a few patients with UC were positive; however, mostly patients with inactive disease appeared to have Blastocystis, while those with flare-ups were negative. Therefore, the influence of dysbiosis on Blastocystis colonisation should be subject to further scrutiny.

A lot of action goes on at the official website for the 1st International Blastocystis Symposium in Ankara in May, with exactly three months to go! Why not take a minute to browse the programme for the Pre-Symposium Course and the Scientific Programme for the actual Symposium? Please go here to familiarise yourself with the new content. 
Also, conference abstracts are pouring in, - did you submit yours yet?


Elghareeb AS, Younis MS, El Fakahany AF, Nagaty IM, & Nagib MM (2015). Laboratory diagnosis of Blastocystis spp. in diarrheic patients. Tropical Parasitology, 5 (1), 36-41 PMID: 25709951

Stensvold, C. (2015). Laboratory diagnosis of Blastocystis spp Tropical Parasitology, 5 (1) DOI: 10.4103/2229-5070.149885  

Pandey PK, Verma P, Marathe N, Shetty S, Bavdekar A, Patole MS, Stensvold CR, & Shouche YS (2015). Prevalence and subtype analysis of Blastocystis in healthy Indian individuals. Infection, Genetics and Evolution: Journal of Molecular Epidemiology and Evolutionary Genetics in Infectious Diseases PMID: 25701123

Rossen NG, Bart A, Verhaar N, van Nood E, Kootte R, de Groot PF, D'Haens GR, Ponsioen CY, & van Gool T (2015). Low prevalence of Blastocystis sp. in active ulcerative colitis patients. European Journal of Clinical Microbiology & Infectious Diseases: Official Publication of the European Society of Clinical Microbiology PMID: 25680316

Wednesday, October 29, 2014

This Month in Blastocystis Research (OCT 2014) - Trick or Treat Edition

Over the past 30 days I've hardly had any time to focus on Blastocystis. I've been busy preparing for and attending UEGWeek 2014, preparing abstracts for next year's ECCMID conference in Copenhagen, and I've also put a lot of effort into preparing proposals for this round of grant calls from the Danish Council for Independent Research

Among other things, we are applying for money to develop DNA-probe based diagnostics, including a unique software, for use in the clinical microbiology lab that entirely circumvents the use of PCR (and thereby amplification bias) and that screens sequence data in real-time. An issue with current state-of-the-art in the area is that no software is available to relevantly and reliably handle the tons of sequence data that next/third/fourth generation sequencing devices are capable of producing. The proposed software will have a vast application range, applicable not only to clinical microbiology but also other areas of microbiology, such as food control, water sanitation, and monitoring of microbes in oil, soil, etc.

We are applying for about 270.000 Euros, and although this doesn't sound like an awful lot of money, competition is extremely fierce for this type of grant (although I'm not sure that the competition has to do exclusively with the scientific and innovative quality of the proposal...). So, let's see if it's going to be trick or treat!

Earlier this month, I was honoured to give a talk in Padova at the XXX National Congress of the Italian Society of Protistology on Blastocystis and its role in health and disease. I also got the chance to listen to some of the remarkable talks delivered by passionate colleagues of the society. There was quite a lot on endosymbionts of protists. The development of mitochondria in eukaryotic cells is a classical example of endosymbiosis; however, there are numerous examples of e.g. bacteria infecting protists, including the parasitic ones. Legionella, for instance, may be found in Acanthamoebaknown to host a variety of bacterial endosymbionts. Along the same lines, I wish that studies could be made to look up potential endosymbionts in Blastocystis; endosymbionts which may confer disease, and the varying/unstable presence of which might explain the irregularity in symptoms reported by Blastocystis carriers? The question about endosymbionts in Blastocystis is interesting not only from a metabolic and horizontal gene transfer point-of-view, but also in the perspective of Blastocystis potentially serving as a vector, a vehicle for transmission of bacteria and maybe viruses... A nice paper on endosymbiotic associations within protists is available for a free download here. Rickettsia, for instance, are obligate intracellular bacteria found as endosymbionts in different types of eukaryotes, including amoebae, but also in endothelial cells (which are not phagocytic by nature, similar - presumably - to the case of Blastocystis), and some of these rickettsia are  known as causes of spotted fever and typhus. I think that Zierdt is the only one until now who has studied endosymbiosis in Blastocystis...

After the congress in Padova, I got a chance to pay my first visit ever to Venice, which was nothing short of brilliant.

Venice, October 2014.

I did have an hour here and there, however, to look up newest 'releases' on Blastocystis, and I'm just going to highlight a few of them.

Unfortunately in Russian and not available for download on any of the servers that I can access, there's a paper describing the finding of dividing (i.e. alive) forms of Blastocystis in a liver abscess in an immunocompromised woman. The question here is of course, did the parasite end up here by chance (fistula and/or secondary to bacterial invasion?) or by independent invasion? Hope to receive a copy of the paper at some point... and a translation!

There is a paper in a journal called 'Case Reports in Medicine' on what is called a co-infection of Schistosoma and Blastocystis in a 37-year-old male with chronic kidney disease, in whom Blastocystis was speculated to be the cause of chronic IBS-like symptoms. However, there is a number of issues that I would like readers of the paper to focus on: Apparently, the patient had Schistosoma mansoni detected in the urine suggesting schistosomiasis of the bladder. But how was Schistosoma detected? It doesn't say. Was it by microscopy? The patient was ab-positive, but still intestinal schistosomiasis was not ruled out (by e.g. PCR on faecal DNA, microscopy for ova and parasites, rectal biopsy, etc.). The patient responded well to praziquantel treatment and got rid of symptoms, including the intestinal symptoms ascribed to Blastocystis, for which the patient was prescribed metronidazole. We know that Blastocystis is only rarely eradicated by metronidazole alone, and indeed, the article does not provide data on post-treatment stool examination to see whether Blastocystis was still there. I think there is a chance that Blastocystis was an incidental finding and that intestinal symptoms in this case were due to Schistosoma. Given our recent data and improved diagnostic techniques, Blastocystis will more often now than ever become an incidental finding on routine analysis of faecal samples.

There is a paper by Fletcher and colleagues coming out in Journal of Public Health Research studying the prevalence and geographical distribution of enteric protozoan infections in Sydney, Australia, which I haven't had a chance to study in detail. I just want to emphasize that this study found Blastocystis prevalence to be increasing by age, a finding adding support to accumulating data suggesting that Blastocystis is more common in adults than in children, which is interesting from a clinical, epidemiological, and ecological point of view.

Hope to be able to address an interesting and brand new paper on Blastocystis treatment in Faculty of 1000 very soon. 

Happy Halloween!


Fletcher S, Caprarelli G, Merif J, Andresen D, Hal SV, Stark D, & Ellis J (2014). Epidemiology and geographical distribution of enteric protozoan infections in Sydney, Australia. Journal of Public Health Research, 3 (2) PMID: 25343139

Nagel R, Bielefeldt-Ohmann H, & Traub R (2014). Clinical pilot study: efficacy of triple antibiotic therapy in Blastocystis positive irritable bowel syndrome patients. Gut Pathogens, 6 PMID: 25349629

Nowack EC, & Melkonian M (2010). Endosymbiotic associations within protists. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 365 (1541), 699-712 PMID: 20124339

Prodeus TV, Zelia OP, Khlebnikova TA, & Pikul' DA (2014). [Extraenteric infection caused by Blastocystis spp. in a female patient with liver abscess]. Meditsinskaia Parazitologiia i Parazitarnye Bolezni (2), 6-9 PMID: 25296418

Young CR & Yeo FE (In Press). Blastocystis and Schistosomiasis coinfection in a patient with chronic kidney disease. Case Reports in Medicine 

Thursday, May 1, 2014

This Month In Blastocystis Research (APR 2014)

Due to all sorts of activities I have not been able to update myself with 'novelties' in the scientific Blastocystis literature lately.

Instead, I would like to highlight two review/opinion papers on the use of PCR-based methods for diagnosis of intestinal parasitic infections in the clinical microbiology laboratory.

Both papers have been published very recently (actually one is still 'in press'). The first is co-authored by Jaco J Verweij and myself, and appears in the April issue of 'Clinical Microbiology Reviews'. This paper aims to provide a relatively systematic review of the extent and relevance of PCR- and sequencing-based methods for diagnosis and epidemiology studies of intestinal parasites, and is as such an inventory of all sorts of DNA-based diagnostic and typing modalities for individual protists and helminths.

The second one is authored solely by Jaco J Verweij and is currently in the 'first online' section in the journal 'Parasitology'. This paper offers a discussion of the application of PCR-based method as a supplementary tool or a substitute for conventional methods (microscopy, antigen detection, etc.). Dr Verweij deals with central questions such as 'Is Molecular Detection Good Enough?' and 'Is Molecular Detection Too Good To Be True?'.

And so these two papers complement each other quite well. For those interested in the very low prevalence of intestinal helminth infections in the Western world, the latter paper has a table which summarizes some quite stunning data.

Although DNA-based methods currently in use do have quite a few limitations, I do believe that for a long while the application of species- and genus-specific PCR methods (real-time PCR, conventional PCR + sequencing, etc.) will appear relevant and state-of-the-art. Dr Verweij, I and a few of our colleagues around the world are currently discussing to which extent next generation sequencing methods can be used to
  • generate data that can assist us in identifying the role of pro- and eukaryote microbial communities in health and disease
  • serve as a tool to generate sequences that can be processed by designated software and thereby identify patterns of microbial communities associated with various disease and health conditions
To this end, at the Laboratory of Parasitology, Statens Serum Institut, we are currently assisting in the development of a software called BIONmeta. BION meta is an open-source package for rRNA based pro- and eukaryote community analysis. Like Qiime and Mothur it is open source but with a growing number of advantages. The package has so far been developed mostly by Niels Larsen (DK), one of the original Ribosomal Database Project authors. It is as yet unpublished, but has been selected for in-house trial-use by companies and institutions that also partly sponsor its development.When relevant, I'll post more information on this software.


Verweij JJ, & Stensvold CR (2014). Molecular testing for clinical diagnosis and epidemiological investigations of intestinal parasitic infections. Clinical Microbiology Reviews, 27 (2), 371-418 PMID: 24696439

Verweij, JJ. (2014). Application of PCR-based methods for diagnosis of intestinal parasitic infections in the clinical laboratory Parasitology, 1-10 DOI: 10.1017/S0031182014000419

Wednesday, December 4, 2013

This Month in Blastocystis Research (NOV 2013)

Few commercial kits are available for detection of Blastocystis. One of them is the ParaFlorB kit developed by Boulder Diagnostics which uses a monoclonal antibody to detect Blastocystis-specific antigen. We are currently testing this kit in our lab, and I hope to be able to get back with a summary of our experience once the evaluation has finished. Another kit is the EasyScreenTM Enteric Parasite Detection Kit (Genetic Signatures, Sydney, Australia), which was recently evaluated by some of my Australian colleagues (Stark et al., 2013). In this case, Blastocystis has been included in a panel testing for 5 parasitic genera, the other ones being Giardia, Cryptosporidium, Entamoeba, and Dientamoeba, which makes it interesting in a clinical microbiology context, - at least for research purposes.

It can certainly be discussed whether both Dientamoeba and Blastocystis should be part of routine screening for single-celled intestinal parasites. For some years, we have included Dientamoeba in a PCR panel also consisting of Cryptosporidium, Giardia and Entamoeba, but we are about to remove it from this panel. This does not mean that we will not be testing for Dientamoeba; it only means that we will offer testing for Dientamoeba as a separate analysis, in line with our tests for Blastocystis.

According to the study, the kit performs quite well with the only major impediment being the fact that it does not enable differentiation between pathogenic and apathogenic species of Entamoeba; another drawback is the fact that it does not enable detection of the more rare protozoa, such as Cystoisospora and Cyclospora (and I would also mention microsporidia and maybe Balantidium coli). Also, I might be a little worried that the kit will not pick up all species and genotypes of Cryptosporidium, - in fact little was done to challenge the kit in the evaluation. Regarding Cryptosporidium, only C. hominis and C. parvum were tested. In Sweden, at least 10% of all human cryptosporidiosis is due to non-hominis and non-parvum species and genotypes. This is an observation that has led me to revisit our own Cryptosporidium real-time PCR. With help from Welsh and Swedish colleagues I managed to establish quite a broad panel of different Cryptosporidium species and genotypes, and much to my surprise, our 'old' real-time PCR failed to detect the vast majority of these... which means that this Cryptosporidium PCR was far from genus-specific. So, I set out to design a genus-specific PCR which is now being integrated with our Giardia real-time PCR in a duplex assay.
Anyway, similar to Cryptosporidium, many species of Blastocystis - the so-called subtypes - can colonise and infect humans. In the evaluation of the EasyScreen kit, only subtypes 1, 3, and 4 were used to challenge the kit, and so, it is not known whether the kit also detects other subtypes found in humans (ST2, ST5, ST6, ST7, ST8, and ST9).

For those interested in these diagnostic multiplex systems, please also visit a previous blog post.

Anastasios Tsaousis and his Canadian group in Halifax had a paper out just now in Eukaryotic Cell expanding their work on the evolution of the cytosolic iron/sulfur cluster assembly machinery in Blastocystis spp. and other microbial eukaryotes. This type of work is crucial for obtaining a deeper understanding of the metabolism of Blastocystis and to understand how it has evolved and how it potentially differs from other eukaryotes.  Apparently, Iron-sulfur cluster-containing proteins and their biosynthetic machinery in single-celled parasites are remarkably different from those in their mammalian hosts and they therefore represent a potentially relevant target for the development of novel chemotherapeutic and prophylactic agents against parasite infections. For those interested in iron-sulfur clusters in protists in general, a review was published in Advances in Parasitology some weeks ago (please see cited literature).

There is paper out on fasciolosis and co-infections, including Blastocystis, and in that paper it appears that nitazoxanide may be able to eradicate Blastocystis. However, only three persons were treated, and I'm not sure that the diagnostic tests used would have picked up light infections of Blastocystis.

Speaking of treatment: Another paper has appeared from the highly productive team in Sydney, - this time on treatment failure in patients with chronic Blastocystis infection and first-authored by Ms Tamalee Roberts, whom I was so fortunate to spend some time with during the recent congress in Copenhagen. The paper is a little difficult to follow, particularly since nothing is mentioned in the Materials and Methods section on the choice of treatment and treatment strategies in general, but then again, the paper is based on a string of individual (groups of) cases with different kinds of treatment approaches and various backgrounds. I really like the fact that the authors are looking at multiple cases and also that have included a few patients receiving the Triple Therapy (nitazoxanide, furazolidone, secnidazole), which appears to have no major clinical efficacy. The paper also confirms the uselessness of metronidazole when it comes to eradicating Blastocystis. What I could have wished for is that the authors had been able to pursue the microbiological effect of treatment in each of the cases; only in some cases do we get to know about clearance/persistence of Blastocystis. Also, here at the SSI we sometimes wonder, whether persistence of symptoms after treatment may in some cases reflect adverse effects of the treatment (including perturbation of intestinal flora), in which case even randomised controlled treatment (RCT) studies are difficult to design and interpret, unless very clear case definitions and inclusion criteria are available. Hence, for RCT studies I think it is pertinent only to include patients with very similar symptoms (and possibly microbiomes!); given the prevalence of Blastocystis, this shouldn't be too difficult.

Regarding my most recent blog post, I have noticed that it caused quite a stir! I did anticipate some kerfuffle though. But fact is that we have gradually been able to collect so much data from different, independent studies, and the trend appears clear. We now need to investigate what this means, and whether this is something that can be exploited.

There will be no DEC 2013 version of 'This Month in Blastocystis Research' - instead I plan on doing a 'Blastocystis Highlights in 2013' post in line with last year's. Suggestions for significant papers/contributions are welcome!

Cited literature:

Ali V, & Nozaki T (2013). Iron-sulphur clusters, their biosynthesis, and biological functions in protozoan parasites. Advances in Parasitology, 83, 1-92 PMID: 23876871

Roberts T, Ellis J, Harkness J, Marriott D, & Stark D (2013). Treatment failure in patients with chronic Blastocystis infection. Journal of Medical Microbiology PMID: 24243286

Stark D, Roberts T, Ellis JT, Marriott D, & Harkness J (2013). Evaluation of the EasyScreen™ Enteric Parasite Detection Kit for the detection of Blastocystis spp., Cryptosporidium spp., Dientamoeba fragilis, Entamoeba complex, and Giardia intestinalis from clinical stool samples. Diagnostic Microbiology and Infectious Disease PMID: 24286625

Tsaousis AD, Gentekaki E, Eme L, Gaston D, & Roger AJ (2013). Evolution of the Cytosolic Iron/Sulfur cluster Assembly machinery in Blastocystis sp. and other microbial eukaryotes. Eukaryotic Cell PMID: 24243793
Zumaquero-Ríos JL, Sarracent-Pérez J, Rojas-García R, Rojas-Rivero L, Martínez-Tovilla Y, Valero MA, & Mas-Coma S (2013). Fascioliasis and intestinal parasitoses affecting schoolchildren in atlixco, puebla state, Mexico: epidemiology and treatment with nitazoxanide. PLoS Neglected Tropical Diseases, 7 (11) PMID: 24278492

Wednesday, September 4, 2013

Yes, we do take orders!

I get an increasing amount of requests for Blastocystis testing (and testing for other parasites as well, for instance Dientamoeba fragilis). Initially, I was happy to do this for free, but now the requests are so regular that I need to add a fee to the tests.

And yes, we do take orders! As the regular reader of this blog would know by now, I run the part of our  Parasitology lab at Statens Serum Institut, Copenhagen, that deals with Blastocystis diagnostics and diagnostics for intestinal parasites in general. I have been developing and optimising molecular Blastocystis diagnostics for years, something which is also witnessed by my scientific production. Please note that we take orders only from health authorities. This means that if you want to have samples tested in our lab, you should contact your GP/specialist/whatever, and have him/her put the order through.

For general screening, I recommend real-time PCR analysis. For evaluation of treatment I recommend adding Blastocystis culture (a positive culture means ongoing Blastocystis infection, while DNA-based tools such as our real-time PCR will detect both dead and live organisms). We also perform subtyping of Blastocystis upon request.

In cases where colleagues want to outsource diagnostic work related to research, we are currently opening up for the possibility of testing large panels of faecal samples (fresh, frozen, or ethanol-preserved) for Blastocystis, Dientamoeba fragilis or other parasites by molecular assays (including DNA extraction) - and - if requested - in combination with traditional microscopy of faecal concentrates.

A selection of our analyses for parasites can be viewed here.

Our parasitology lab is merged with the mycology lab, and therefore we have plenty of opportunity to test the same stool sample for parasites and yeasts (e.g. Candida), if requested. As a new feature, Blastocystis+Dientamoeba+Candida analyses can now be requested in combination as a 'package' with a discount. We are happy to send out test tubes and transport envelopes, but I repeat that charges will apply.

Research-wise, we are currently taking different approaches to detecting and differentiating non-human eukaryotic DNA/RNA in human faecal samples, among these the GUT 18S approach.

For further inquiries and information, please do not hesitate to contact me (contact details can be found here).

Relevant articles on molecular diagnostics for Blastocystis detection and subtyping:

Stensvold CR, Ahmed UN, Andersen LO, & Nielsen HV (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 PMID: 22422846

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

Friday, August 30, 2013

This Month In Blastocystis Research (AUG 2013)

Quite a few papers relevant to Blastocystis research have made it to PubMed over the past month! Therefore, the August version of 'This Month in Blastocystis Research' is more like a list of papers + short descriptions/comments, rather than one or two actual paper reviews.

Dr Aldert Bart and his Dutch colleagues have published a study that confirms data emerging from other parts of Europe. Using microscopy (fixed faecal smears) and PCR, they found an almost 40% prevalence of Blastocystis in returning travelers with symptoms, and a prevalence of 18% in patients referred for other reasons. The distribution of subtypes found in the study population was quite similar to what has been found elsewhere in Europe with ST3 predominating (42%) and the rest of the subtypes attributable to ST1 (22%), ST2 (22%), ST4 (12%), ST6 (1%) and ST7 (1%).

The Tropical Parasitology theme issue on Blastocystis has now gone live. You’ll find a link to the editorial and the three papers included in the symposium here.

In my previous post I referred to a new study from Colombia which includes subtyping of Blastocystis isolates from humans, and a variety of animals, including birds. The paper is interesting for a number of reasons, but first and foremost it confirms the virtual absence of ST4 in humans in S America. Moreover, the study included 70 Blastocystis positive samples from asymptomatic carriers, 40 positive samples from patients with diarrhoea, and 15 positive samples form patients with IBS. Remarkably, all samples from healthy carriers were typed as ST1, those from patients with diarrhoea belonged to ST2, and those from IBS patients to ST3. Such a clear-cut distribution of subtypes across cohorts is unprecedented and of course warrants confirmation and further investigation. In Europe, ST4 is very common in humans, while it appears rare in humans in many other parts of the world. ST4 also appears rare among non-human primates (NHPs), our closest living relatives, and while NPHs and humans otherwise tend to share the same major subtypes (ST1, ST2, and ST3), this suggests that while subtypes 1, 2 and 3 have probably co-evolved with primates, ST4 has only recently entered the primate population with a preference for humans! I have hinted at this many times by now, but I find it extremely interesting which is why I keep repeating it.

There is a paper out by Santos and Rivera from the Philippines comparing microscopy of direct faecal smear with culture and PCR for detection of Blastocystis. They ended up concluding that culture was the best diagnostic modality, but it should be noted that the PCR used in the study targets a 1.8 kbp product (complete SSU rRNA gene!), and much smaller products are usually targeted in diagnostic PCR assays. The Blastocystis real-time PCR developed by me and my colleagues targets a sequence stretch of ~120 bp, securing optimum test sensitivity. The results of the Philippine study should be interpreted with this in mind.

Li et al., have published data on experimental infection of ST1 in Sprague-Dawley rats. Animals belonging to this species appeared susceptible to a ST1 strain isolated from a diarrhoeic patient that had been kept in culture and for which induction of cysts had been performed with a view to infecting the rats. The study confirms that Blastocystis is mainly a parasite of the coecum and colon. The authors found evidence of Blastocystis invasion into the lamina propria in one of the animals, and signs of inflammation in all animals challenged. While it is great to see that experimental models can be sustained and that encystation can be induced in vitro, at least two important factors must be kept in mind to fully comprehend the study: Although cysts were isolated by gradient centrifugation prior to inoculation, it is unlikely that all bacteria have been removed from cyst suspensions; in other words, the cyst preparation is not likely to be 'sterile', and any effect of the potentially accompanying bacterial flora is difficult to determine. Moreover, rats may not be natural hosts of ST1 (very few data available on the topic!), and so, the pathology caused in the rats may be an unlikely finding in humans, who are indeed natural hosts of ST1 and may have developed a high degree of tolerance to this subtype.

Are dogs, wolves, and other canids natural hosts of Blastocystis?

When visiting Australia earlier this month, I had the pleasure of meeting Wenqi Wang and Tawin Inpankaew, both PhD students working at School of Veterinary Science, The University of Queensland Gatton Campus and supervised by Dr Rebecca Traub. One of the foci of this group is to study Blastocystis in animals, for instance in households where animals are kept as pets. Recently, a paper emerged from this group on diversity of Blastocystis subtypes in dogs in different geographical settings, hence domestic/pound dogs from Brisbane, Australia, semi-domesticated dogs from a village in Cambodia, and stray dogs from Mumbai and other Indian cities. Using sensitive PCR methods they observed that almost one fourth of the Indian dogs were infected, while dogs in the Cambodian village and in Queensland remained largely uninfected. Coprophagy and access to Blastocystis-positive stool from different hosts may account for the relatively high prevalence in stray dogs in India, although one might assume that the prevalence would then be even much higher? The team used nested PCR in their study and found four different subtypes in the Indian dogs, including ST1, ST4, ST5 and ST6. Whether all of their data collectively indicate that dogs are not natural hosts of Blastocystis is a matter of debate and remains to be more thoroughly investigated. Indeed, prevalence and subtype data from studies of samples from wild life canids (dingos, jackals, wolves, coyotes, but also foxes and raccoon dogs) would shed further light on this topic.

Finally, for those interested in how Blastocystis deals with oxidative stress and related metabolic issues, there is a paper out on iron-sulphur cluster biogenesis in protozoan parasites by Ali and Nozaki citing works by Tsaousis (2012), Denoeud (2011), Long (2011), and Stechmann (2008).


Ali V, & Nozaki T (2013). Iron-sulphur clusters, their biosynthesis, and biological functions in protozoan parasites. Advances in Parasitology, 83, 1-92 PMID: 23876871

Bart A, Wentink-Bonnema EM, Gilis H, Verhaar N, Wassenaar CJ, van Vugt M, Goorhuis A, van Gool T. Diagnosis and subtype analysis of Blastocystis sp. in patients in a hospital setting in the Netherlands. BMC Infectious Diseases, 13:289.

Li J, Deng T, Li X, Cao G, Li X, & Yan Y (2013). A rat model to study Blastocytis subtype 1 infections. Parasitology Research PMID: 23892480 DOI: 10.1007/s00436-013-3536-7

Parija SC (2013). Blastocystis: Status of its pathogenicity. Tropical Parasitology, 3 (1) PMID: 23961433

Parija SC, & Jeremiah S (2013). Blastocystis: Taxonomy, biology and virulence. Tropical Parasitology, 3 (1), 17-25 PMID: 23961437 

Ramírez JD, Sánchez LV, Bautista DC, Corredor AF, Flórez AC, & Stensvold CR (2013). Blastocystis subtypes detected in humans and animals from Colombia. Infection, Genetics and Evolution : Journal of Molecular Epidemiology and Evolutionary Genetics in Infectious Diseases PMID: 23886615

Sekar U, & Shanthi M (2013). Blastocystis: Consensus of treatment and controversies. Tropical Parasitology, 3 (1), 35-9 PMID: 23961439

Stensvold CR (2013). Blastocystis: Genetic diversity and molecular methods for diagnosis and epidemiology. Tropical Parasitology, 3 (1), 26-34 PMID: 23961438  

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

Wednesday, July 10, 2013

This Month In Blastocystis Research (JUL 2013)

The open access journal 'Tropical Parasitology' (published by the Indian Academy of Tropical Parasitology) has included a symposium on Blastocystis in their January-June (Vol. 3) issue (available here). The symposium comprises three papers; one is on "taxonomy, biology and virulence", the next is on genetic diversity and molecular methods for diagnosis and epidemiology, and the last one is on treatment controversies. I believe that it may take quite a while before these papers will appear in PubMed.

The first paper written by Drs Parija and Jeremiah sums up a few of the aspects related to (especially historical) taxonomic issues and very little on the actual biology of Blastocystis. Meanwhile, there is quite a substantial section on Blastocystis morphology. Regarding virulence, the authors mention the possibility that differences in virulence may be due to differences in subtypes, but that subtyping alone does not predict pathogenicity which in part may be due to varying levels of intra-subtype genetic variation. The authors also briefly mention some of the morphological and phenotypical observations that have been associated with 'pathogenic Blastocystis', such as the amoeboid stage, large cells, rough surface, slow growth rate, and increased binding to lectins. It is always interesting to speculate on such associations, but it must be kept in mind that results from in-vitro experiments may not necessarily reflect in-vivo situations.

One topic that keeps popping up in the literature - and also in two of the papers here in this symposium - is the possibility of 'amoebic forms' of Blastocystis being associated with symptomatic infection. This hypothesis was introduced in 2006 by Tan and Suresh, I believe; Scanlan (2013) speculated that amoeboid forms might be the nutrient acquiring form potentially selecting for bacterial virulence or certain bacterial communities through grazing; please go here for more thoughts from a previous blog post.

My own experience on Blastocystis morphology mainly stems from looking at cultures, and since we practically only get isolates from patients with gastrointestinal disease, I don't know what Blastocystis cultures from asymptomatic individuals look like. A dear colleague of mine - Marianne Lebbad, a brilliant Swedish parasitologist with many years in business - sent me the picture below (light microscopy of a faecal concentrate) and speculates that Blastocystis might be able to form groups/clusters of cells, maybe even with the ability to form a mono-layer on the surface of the gut mucosa? I've never observed the cluster formation in cultures, but then again, we have no idea of whether the stages seen in in vitro cultures (microaerophilic environment) are identical to the in vivo stages (strictly anaerobic), and exactly how Blastocystis lives and multiplies in the colon... Anyway, the idea of biofilm comes into mind. It would be nice to learn more from colleagues with a similar experience.

Light microscopy of Blastocystis apparently forming a cluster of cells; we wonder whether the cells are in fact 'glued' together and if so, how? Courtesy of Dr Marianne Lebbad.

Moving on to the next paper, this one was written by me and deals mostly with issues and developments within the field of diagnostics, molecular characterisation, and molecular epidemiology. The target audience comprises clinical microbiologists and those involved in Blastocystis epidemiology and genetic diversity research. Included is a table, which is basically a reproduction of the one included in the recent paper by Alfellani et al. (2013) displaying the distribution of subtypes in humans across different geographical regions. I hope that the open access feature of this paper will prompt even more researcher into Blastocystis epidemiology! At least it is currently listed on the site as 'popular'!

The third paper in the string is written by Drs Sekar and Shanthi. These authors put emphasis on the conspicuous lack of data on the metabolic processes of Blastocystis, making it difficult to establish how to best approach antibiotic intervention; we must anticipate that with more genomic and transcriptomic data analyses arriving within a foreseeable future we will soon know much more about this. They also reiterate what has been put forth by many, namely that differences in eradication may boil down to differences in drug susceptibility, which again may be due to a variety of reasons, including genetic diversity, which is extreme in Blastocystis.

According to these authors, 'therapy should be limited to patients with persistent symptoms subsequent to a complete work up for alternative etiologies'; at the present stage this appears sensible, although clinicians would probably appreciate a clearer definition of 'symptoms'!

The review goes through some of the drugs most commonly used for treating Blastocystis, including metronidazole, paromomycin and co-trimoxazole, but also includes a few data on the use of the probiotic Saccharomyces boulardii in attempts to eradicate Blastocystis. There is not very much on the mechanisms of drug action, - it's more like a summary of data coming out from different studies, including the few placebo-controlled ones.
Regarding co-trimoxazole (which is also known as 'Bactrim' or 'Septra') this drug combo is often administered to HIV-patients prophylactically against Pneumocystis. In a study of parasites in Danish HIV patients, only 6/96 patients were given co-trimoxazole (unpublished data); two of these patients had Blastocystis. Hence, one 'alternative' way of finding out about the efficacy of co-trimoxazole on Blatocystis is to test the stools from patients undergoing long-term Pneumocystis prophylaxis comparing these patients to a cohort not receiving Pneumocystis prophylaxis but otherwise similar.

I find it a bit peculiar though to go through a review on treatment data that does not at one single point mention the need for sensitive diagnostics when evaluating courses of treatment and the identification of carriers and non-carriers. Also, there are some passages which are quite difficult for me to follow, for instance p. 36, second column, bottom section.

I hope that this symposium will inspire some of our colleagues and contribute to an increased understanding of Blastocystis.



Parija SC & Jeremiah SS (2013). Blastocystis: Taxonomy, biology and virulence Tropical Parasitology DOI: 10.4103/2229-5070.113894
Stensvold CR (2013). Blastocystis: Genetic diversity and molecular methods for diagnosis and epidemiology Tropical Parasitology DOI: 10.4103/2229-5070.113896  

Sekar U & Shanthi M (2013). Blastocystis: Consensus of treatment and controversies Tropical Parasitology DOI: 10.4103/2229-5070.113901


Scanlan PD (2012). Blastocystis: past pitfalls and future perspectives. Trends in parasitology, 28 (8), 327-34 PMID: 22738855

Stensvold CR, Nielsen SD, Badsberg JH, Engberg J, Friis-Møller N, Nielsen SS, Nielsen HV, & Friis-Møller A (2011). The prevalence and clinical significance of intestinal parasites in HIV-infected patients in Denmark. Scandinavian Journal of Infectious Diseases, 43 (2), 129-35 PMID: 20936912  

Tan TC & Suresh KG (2006). Predominance of amoeboid forms of Blastocystis hominis in isolates from symptomatic patients. Parasitology Research, 98 (3), 189-93 PMID: 16323025