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.

A Penny For Your Thoughts

So, what should we do about Blastocystis? What do we want to know?

I believe the imminent answer to the latter question is easy: We want to know whether it’s pathogenic, whether we should treat it and how. But I also think that there are many other interesting aspects of Blastocystis which are also of broad interest to the general public, namely: How about the many cases of asymptomatic Blastocystis carriage? What does Blastocystis do in our guts? Could it have any potentially beneficial impact on our health?

Given the fact that Blastocystis has not been implicated in any outbreaks (admittedly: I guess that no one actually ever looked for Blastocystis in outbreak investigations... except for me!), I reckon that the chance of it being involved in acute diarrhoea is small. So, in that respect it's very different from the other intestinal protists such as Giardia, Cryptosporidium, Cyclospora, microsporidia, even Entamoeba histolytica. It's actually more reminiscent of helminth infections, which are are often chronic, and when light hardly give rise to symptoms (depending on species that is!).So I'm more thinking along the lines of co-evolution, adaptation, etc.

Maybe future research will call for a shift in paradigm, but until then I think that we should do what we already can, just at a larger scale and see where it takes us, namely:

Where Are We On Blastocystis Subtypes?

As mentioned, Blastocystis exhibits remarkable intrageneric diversity, which is continuously being explored by us and our colleagues. We are convinced that the genus of Blastocystis comprises multiple species, but for now we call them "ribosomal lineages" or "subtypes" and allocate numbers to each subtype, hence ST1, ST2, etc. While the number of subtypes that can be found in humans remains stable, we and our colleagues are still expanding the subtype universe in non-human hosts (I will be blogging on this shortly).

Barcoding currently represents state-of-the-art in Blastocystis subtyping, and luckily this method appears to gain a foothold in labs across the world.

Nine subtypes have been found in humans, but some of them only on rare occasions. A recent study going out from London School of Hygiene and Tropical Medicine and led by Dr Alfellani and published just now in Acta Tropica looked at 356 Blastocystis sequences from samples from the UK and Libya, but also from sub-Saharan Africa, namely Liberia and Nigeria.

The "Flagyl" Poll

For some reason the "Flagyl" poll in the right side bar of this blog was reset; the number of votes was approaching 100. The question was

"For those who have received metronidazole (Flagyl or Protostat) treatment for Blastocystis, please indicate whether you experienced no, transient or permanent improvement (or none of the above)"

The interesting thing is that there was a tie between "no improvement" and "transient improvement", and although this poll could have been heavily biased in numerous ways, it is still completely in line with our experience: Many patients report transient alleviation of symptoms, while others have no clinical benefit from Flagyl. Flagyl is an antibiotic targeting a wide range of bacteria and single-celled parasites. It is sometimes successful in terms of eradicating Dientamoeba fragilis, one of the most common parasites in the human intestine, and a parasite which may cause symptoms especially in children (we are currently conducting a randomised control clinical trial at Statens Serum Institut to explore clinical and microbiological effect of metronidazole treatment of children with D. fragilis).

Many people will get diagnosed with Blastocystis without knowing whether they might also be positive for D. fragilis (and vice versa). It is a complex situation, since both parasites are common, they are difficult to detect unless you use PCR or other specialised analyses, and in most labs they are not tested for on a routine basis. And if they happen to be part of the panel of organisms that is tested for, it may be so that insensitive methods are used for their detection, which means that only a fraction of the cases will be detected. So, this is a bit of a conundrum in itself!

So, it's not easy to know what causes the temporary alleviation in some patients. Is it due to parasite recrudescence? Is it due to parasite eradication with subsequent re-infection? And which parasite? Blastocystis? Dientamoeba? Any others? Or, is it due to perturbation of the intestinal flora in a "positive" direction, which is then gradually going back to normal? Placebo effect? There are possibly many more explanations...

However, deep sequencing of faecal samples pre- and post treatment of parasite-positive patients will probably answer many of our questions...

Literature:

Engsbro AL, Stensvold CR, Nielsen HV, & Bytzer P (2012). Treatment of Dientamoeba fragilis in Patients with Irritable Bowel Syndrome. The American journal of tropical medicine and hygiene PMID: 23091195

Engsbro AL, & Stensvold CR (2012). Blastocystis: to treat or not to treat ... But how? Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 55 (10), 1431-2 PMID: 22893582

The Potential Role of Our Microbiome Ecosystems

For those who like these pop-sci articles on the still somewhat conjecture-like but very inspiring theories about the role of our intestinal microbiome in health and disease, here's a link to an article from The Economist (18 AUG 2012):

The Human Microbiome: Me, myself, us

And let me reiterate: We still don't know much about mikro-eukaryotes in all this... do they play a role as well? And how do they cope with different types of microbiomes?

Anyways, enjoy!

To Treat or Not To Treat... But How?

In the "To Treat or Not To Treat" series (please look up previous post here), we have come to the "...But How?" episode.

Blastocystis may be susceptible to a number of drugs - in vitro. In vitro is not the opposite of in vivo. In vitro just  means that the test has been done on an organism that has been isolated from its usual habitat and tested e.g. in a flask, test tube, etc. In the lab, strains can be challenged and manipulated in multiple ways, but there is no guarantee that the outcome of an in vitro susceptibility test is reproducible in vivo, i.e. when the organism is challenged in its natural habitat and under "natural" conditions. Hence, if you test Blastocystis against metronidazole or any other compound (such as iodine) in vitro, and you observe an effect, you cannot rely on being able to reproduce the effect in vivo. This is due to a variety of reasons including pharmaco-kinetics and pharmaco-dynamics, including the ability of the drug to reach the parasite in its ecological niche, impact of the drug on other micro-organisms, drug interactions, strain-dependent differences in susceptibility (including inherent or acquired resistance), etc.

We recently described a case in which a woman with irritable bowel syndrome (according to the Rome III criteria) had both Blastocystis subtype 9 (ST9) and Dientamoeba fragilis. In order to try and eradicate the parasites and to see whether any eradication would impact on her clinical situation, she received multiple courses of antibiotic treatment:

1. Metronidazole (750 mg x 3/d for 10 days)
2. Tetracycline (500 mg x 4/d for 10 days)
3. Trimethoprim + Sulfamethoxazole (TMP 800 mg + SXT 160 mg x 2/d for 7 days)
4. Mebendazole + Metronidazole (100 mg x 2 separated by 2 weeks; subsequently metronidazole as in 1.)
5. Paromomycin + Metronidazole (PM 500 mg + MZ 170 mg x 3/d for 10 days)

Mebendazole was given to the entire household due to suspicion of pinworm infection running in the family that could be a potential reservoir of D. fragilis (re-)infection.

No clinical alleviation was seen throughout this period.

PCR-based detection of Blastocystis and D. fragilis was used to evaluate  faecal samples 5-10 days post-treatment: Microbiological effect was seen only on D. fragilis which was cleared only after treatment with PM + MZ (5).

So, Blastocystis "survived" this series of antimicrobial treatment. In Denmark, no further relevant treatment options are available for general use (actually, even the use of Humatin (PM) needs a special license).

None of the patient's family members or pets were found to be colonised by the same strain, probably indicating that there was no "local" reservoir for ST9, and that the repeated finding of ST9 was not due to re-infection.

It may be so that Blastocystis requires a certain intestinal bacterial flora to establish. However, we expect that substantial perturbations in the intestinal flora must have taken place during the patient's various treatments, and therefore Blastocystis must be able to quickly overcome and adapt to such perturbations. It may add to the conundrum that in this case the woman harboured ST9, which is only very rarely seen in humans, and we might therefore deduce that its presence would be more volatile. No animal/environmental reservoir has yet been identified for ST9.

There is no doubt that microbiomic profiling of the intestinal flora would be of great benefit in a case like this. If data could be achieved on the impact of these drugs on the relative bacterial structure and function by metagenomic approaches, then this would allow us to explore the changes in the general flora that Blastocystis is capable of withstanding. Certainly, none of these drugs had a measurable in-vivo protistocidal effect on Blastocystis when administered as shown.

I re-emphasise that it is far from certain that Blastocystis is capable of inducing disease, directly or indirectly, and hence, we do not know if, and in which situations, we should aim at eradicating it. Suffice it to say, that in our hands and with the compounds that are available for general use in Denmark, it is apparently extremely challenging to eradicate Blastocystis, if at all possible.

Microbe Resilience (Source)

Further reading:

Coyle CM, Varughese J, Weiss LM, & Tanowitz HB (2012). Blastocystis: to treat or not to treat... Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 54 (1), 105-10 PMID: 22075794

Engsbro AL, & Stensvold CR (2012). Blastocystis: To Treat Or Not To Treat...But How? Clinical infectious diseases : an official publication of the Infectious Diseases Society of America PMID: 22893582

Stensvold CR, Smith HV, Nagel R, Olsen KE, & Traub RJ (2010). Eradication of Blastocystis carriage with antimicrobials: reality or delusion? Journal of clinical gastroenterology, 44 (2), 85-90 PMID: 19834337

Intestinal Symptoms

For over a century, the clinical significance of Blastocystis has puzzled medical doctors scientists. After realising the extensive genetic diversity in Blastocystis, one of the current main hypotheses is that Blastocystis subtypes differ in terms of clinical significance. In other words: Symptoms, such as diarrhoea or other intestinal upset, may be associated only with one or more subtypes, while other subtypes are strict commensals.

Blastocystis is very difficult to eradicate and colonisation is chronic. Do symptoms caused by potentially  pathogenic subtypes persist or do they develop initially only to diminish after host immunological adaptation? Do fluctuations in symptoms reflect fluctuations in parasite load? Such issues ire important when interpreting results generated from cross-sectional surveys of subtypes in various cohorts.
Moreover, intestinal symptoms are difficult to define. Diarrhoea may be defined by 3 stool passages per day or more, while many other symptoms can be very difficult to define, if at all possible. Irritable bowel syndrome (IBS) and - to some extent - food allergy may both be considered differential diagnoses of symptomatic Blastocystis infections.

IBS diagnosis is currently defined by the Rome III criteria, and there are at least three types of IBS, namely IBS with diarrhoea, IBS with constipation and IBS with a mixture of diarrhoea and constipation.

Symptoms may be experienced differently from person to person. While abdominal cramping is perceived mostly as a symptom and something unpleasant, flatulence may by many be seen as a sign of a "healthy tummy" (e.g. due to consumption of a high fibre diet), although "inconvenient". Some individuals may very well tolerate intermittent intestinal symptoms and do not consult their GPs or other health care professionals, while others may be much more sensitive to any changes in for instance stool patterns.

What some people do not realise is that many methods fail to detect Blastocystis. PCR and culture are the most sensitive methods, but are still only rarely used. Moreover, PCR is also suitable for the detection of Dientamoeba fragilis, which is a parasite often seen in co-infection with Blastocystis. These two parasites are probably the most common single-celled eukaryotes in the human intestine.

This means that complete and accurate microbiological make-ups are far from always performed. And so, incomplete microbiological examination coupled with differential diagnostic challenges, potential immunological adaptation and the very subjective components of symptom presentation renders our quest for clear-cut associations extremely challenging. Blastocystis will often be seen as the culprit of symptoms, possibly simply to the reason that it is the only potential microbial pathogen that has been demonstrated in a stool sample. Cohort studies using sensitive diagnostic methods for pathogen surveillance are expensive, but may be one of the few only ways forward with regard to epidemiological studies that can assist us in resolving the clinical significance of Blastocystis.