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Episode 36: Uncovering the mechanisms of sorbitol intolerance, with Dr. Jee-Yon Lee MD PhD

/in Podcast, Season Three /by Laura

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This episode features Jee-Yon Lee MD PhD, assistant project scientist at the University of California Davis, USA, speaking about a recent paper on the mechanisms of sorbitol intolerance and the contributions of the gut microbiota. Dr. Lee explains how gut microbes in the large intestine can drive sorbitol intolerance, and how their research group designed a probiotic intervention to ameliorate it in a mouse model.

Key topics from this episode:

  • Dr. Lee joined Baumler lab in 2017 to study how ecological causes such as diet or chronic disease can change host cell metabolism, thereby changing the gut microbiota, and also the effect of the gut microbiota on chronic diseases.
  • Sorbitol is a sugar alcohol used as an artificial sweetener. It cannot be absorbed or catabolized in the small intestine so it reaches the large intestine and draws water into the lumen through osmosis. Large amounts cause diarrhea, but normally small amounts do not. 
  • Some people are sensitive to small amounts of sorbitol and are said to have sorbitol intolerance. Where does the intolerance originate? Possibly the inability of bacteria in the large intestine to catabolize sorbitol using enzymes.
  • Sorbitol intolerance (causing diarrhea) can be transient, such as after taking antibiotics. 
  • What is happening in sustained sorbitol intolerance? Clinically, a recent history of taking antibiotics plus a high-fat diet is associated with diarrhea as well as low-grade inflammation. A mouse model showed that a high-fat diet plus antibiotics led to low-grade inflammation, which may be at the root of sorbitol intolerance.
  • Clostridia are the main bacteria catabolizing sorbitol in the gut. Overall, a high-fat diet plus antibiotics together drive the gut ‘dysbiosis’, and contribute to the chronic depletion of mitochondrial function in the colonic epithelium. This makes the colonic environment less hypoxic, sustains the depletion of Clostridia, and thereby induces sorbitol intolerance.
  • From this, Dr. Lee helped design a probiotic intervention. They selected 3 strains of bacteria and tested them with the high-fat diet and antibiotics mouse model. All of them protected the host from sorbitol intolerance in slightly different ways.
  • Decreased sorbitol dehydrogenase activity may be a biomarker of sorbitol intolerance; currently there’s no way to diagnose this intolerance clinically, so patients typically cut out the substance to discover their intolerance.

Episode abbreviations and links:

About Dr. Jee-Yon Lee MD PhD:

Jee-Yon Lee is an Assistant Project Scientist in Dr. Andreas Baumler’s lab at UC Davis, focusing on studying host-microbial interactions and their impact on human health and non-communicable diseases. She earned her MD and PhD from Yonsei University College of Medicine and served as a family medicine physician in South Korea until 2017. She joined Dr. Andreas Baumler’s lab in 2017 as a visiting scholar and completed her postdoctoral research there. Dr. Lee’s long-term research goal is to elucidate the ecological causes of dysbiosis, its consequences on the development of human diseases, and to find potential therapeutics targeting the microbiome.

Probiotics vs. prebiotics: Which to choose? And when?

/in Consumer Blog, ISAPP Science Blog /by KC

By Dr. Karen Scott, PhD, Rowett Institute, University of Aberdeen, Scotland

As consumers we are constantly bombarded with information on what we should eat to improve our health. Yet the information changes so fast that it sometimes seems that what was good for us last week should now be avoided at all costs!

Probiotics and prebiotics are not exempt from such confusing recommendations, and one area lacking clarity for many is which of them we should pick, and when. In this blog I will consider the relative merits of probiotics and prebiotics for the gut environment and health.

By definition, both probiotics and prebiotics should ‘confer a health benefit on the host’. Since an improvement in health can be either subjective (simply feeling better) or measurable (e.g. a lowering in blood pressure) it is clear that there is not a single way to define a ‘health benefit’. This was discussed nicely in a previous blog by Prof Colin Hill.

Although consumption of both probiotics and prebiotics should provide a health benefit, this does not mean that both need to act through the gut microbiota. Prebiotics definitively need to be selectively utilised by host microorganisms – they are food for our existing microbiota. However, depending on the site of action, this need not be the gut microbiota, and prebiotics targeting other microbial ecosystems in or on the body are being developed. Traditionally prebiotics have specifically been used to boost numbers of gut bacteria such as Bifidobacterium and the Lactobacilliaceae family, but new prebiotics targeting different members of the gut microbiota are also currently being researched.

Probiotics are live bacteria and despite a wealth of scientific evidence that specific probiotic bacterial strains confer specific health benefits, we often still do not know the exact mechanisms of action. This can make it difficult both to explain how or why they work, and to select new strains conferring similar health benefits. Many probiotics exert their effects within the gut environment, but they may or may not do this by interacting with the resident gut microbiota. For instance probiotics that reduce inflammation do so by interacting directly with cells in the mucosal immune system. Yet strains of lactobacilli (see here for what’s included in this group of bacteria) may do this by modulating cytokine production while Bifidobacterium strains induce tolerance acquisition. These very different mechanisms are one reason why mixtures containing several probiotic species or strains may in the end prove the most effective way to improve health. On the other hand, some probiotics do interact with the resident gut microbes: probiotics that act by inhibiting the growth of pathogenic bacteria clearly interact with other bacteria. Sometimes these may be potential disease-causing members of the resident microbiota, normally kept in check by other commensal microbes that themselves have become depleted due to some external impact, and some may be incoming pathogens. Such interactions can occur in the gut or elsewhere in the body.

This brings me back to the original question, and one I am frequently asked – should I take a probiotic or a prebiotic? The true and quick answer to this question is ‘it depends’! It depends why you are asking the question, and what you want to achieve. Let’s think about a few possible reasons for asking the question.

I want to improve the diversity of my microbiota. Should I take a prebiotic or a probiotic?

My first reaction was that there is an easy answer to this question – a prebiotic. Prebiotics are ‘food’ for your resident bacteria, so it follows that if you want to improve the diversity of your existing microbiota you should take a prebiotic. However, in reality this is too simplistic. Since prebiotics are selectively utilised by a few specific bacteria within the commensal microbiota to provide a health benefit, taking a prebiotic will boost the numbers of those specific bacteria. If the overall bacterial diversity is low, this may indeed improve the diversity. However, if the person asking the question already has a diverse microbiota, although taking one specific prebiotic may boost numbers of a specific bacterium, it may not change the overall diversity in a measurable way. In fact the best way to increase the overall diversity of your microbiota is to consume a diverse fibre-rich diet – in that way you are providing all sorts of different foods for the many different species of bacteria living in the gut, and this will increase the diversity of your microbiota.  Of course, if you already consume a diverse fibre-rich diet your microbiota may already be very diverse, and any increased diversity may not be measurable.

I want to increase numbers of bifidobacteria in my microbiota. Should I take a prebiotic or a probiotic?

Again, I initially thought this was easy to answer – a prebiotic. There is a considerable amount of evidence that prebiotics based on fructo-oligosaccharides (FOS or inulin) boost numbers of bifidobacteria in the human gut. But this is only true as long as there are bifidobacteria present that can be targeted by consuming suitable prebiotics. Some scientific studies have shown that there are people who respond to prebiotic consumption and people who do not (categorised as responders and non-responders). This can be for two very different reasons. If an individual is devoid of all Bifidobacterium species completely, no amount of prebiotic will increase bifidobacteria numbers, so they would be a non-responder. In contrast if someone already has a large, diverse bifidobacteria population, a prebiotic may not make a meaningful impact on numbers – so they may also be a non-responder.

However, for those people who do not have any resident Bifidobacterium species, the only possible way to increase them would indeed be to consume a probiotic- specifically a probiotic containing one or several specific Bifidobacterium species. Consuming a suitable diet, or a prebiotic alongside the probiotic, may help retention of the consumed bifidobacteria, but this also depends on interactions with the host and resident microbiota.

I want to increase numbers of ‘specific bacterium x’ in my microbiota. Should I take a prebiotic or a probiotic?

The answer here overlaps with answer 2, and depends on the specific bacterium, and what products are available commercially, but the answer could be to take either, or a combination of both – i.e. a synbiotic.

If bacterium x is available as a probiotic, consuming that particular product could help. If bacterium x has been widely researched, and the specific compounds it uses for growth have been established, identifying and consuming products containing those compounds could boost numbers of bacterium x within the resident microbiota. Such research may already have identified combination products – synbiotics – that could also be available.

One caveat for the answers to questions 2 and 3 is that probiotics do not need to establish or alter the gut microbiota to have a beneficial effect on health. In fact, a healthy large intestine has a microbial population of around 1011-1012 bacterial cells per ml, or up to 1014 cells in total, while a standard pot of yogurt contains 1010 bacterial cells (108 cells/ml). Assuming every probiotic bacterial cell reaches the large intestine alive, they would be present in a ratio of 1: 10,000. This makes it difficult for them to find a specific niche to colonise, so consuming a probiotic may not “increase numbers of ‘specific bacterium x’ in my microbiota”, but this does not mean that the function of the probiotic within the gut ecosystem would not provide a health benefit. Many probiotics act without establishing in the microbiota.

I’ve been prescribed antibiotics. Should I take a prebiotic or a probiotic?

In this case the answer is clear cut – a probiotic.

There is a lot of evidence that consumption of probiotics can alleviate symptoms of, or reduce the duration of, antibiotic associated diarrhoea. From what we know about mechanisms of action, consumption of antibiotics kills many resident gut bacteria, reducing the overall bacterial population and providing an opportunity for harmful bacteria to become more dominant. Consuming certain probiotics can either help boost bacterial numbers in the large intestine, preventing the increased growth in pathogenic bacteria until the resident population recovers, or can increase production of short chain fatty acids, decreasing the colonic pH, preventing growth of harmful bacteria. Ideally probiotics would be taken alongside antibiotics, from day 1, to avoid the increase in numbers of the potentially harmful bacteria in the first place. This has been shown to be more effective. Consuming the probiotic alongside prebiotics that could help the resident microbiota recover more quickly may be even more effective. Even if you’ve already started the course of antibiotics, it’s not too late to start taking probiotics to reduce any side-effects. Always remember to complete taking the course of antibiotics as prescribed.

 

 

Putting all of this together to answer the initial question of whether it’s better to take probiotics or prebiotics, a better answer may in fact be take both to cover the different effects each has, maximising the benefit to health. There are specific times when probiotics are better, and other times when prebiotics are better, and consuming both together may make each more effective. In any case care has to be taken to consume a product that has been confirmed through robust studies to have the specific benefit that is required.

 

Do antibiotics ‘wipe out’ your gut bacteria?

/in Consumer Blog, ISAPP Science Blog /by KC

By Dr. Karen Scott, University of Aberdeen, UK

Antibiotics have been an important tool in medicine to kill pathogenic bacteria and treat infectious diseases for many decades. But for most of those decades, scientists had limited awareness of the community of ‘good’ microbes that reside in our guts and other parts of the body. Now that we have ample evidence of the beneficial functions of these abundant resident microbial communities, we need to be aware of the potential impact antibiotics may have on them – and whether antibiotics might wipe them out, creating a different health problem.

Antibiotics act against basic cellular functions of microbes – targeting cell wall synthesis, DNA/RNA synthesis, protein synthesis and folate synthesis. In order to avoid the effects of the antibiotics, bacteria can either alter their own target molecule so that the antibiotic is ineffective, actively pump the antibiotic out of the cell, or inactivate the antibiotic. With bacteria constantly trying to survive in the face of antibiotics, we are in a continuous race to ensure that the disease-causing bacteria we are trying to eliminate remain susceptible to the antibiotics used to treat them.

The action of antibiotics against bacteria can be classified according to:

  • Bacteriostatic (inhibiting growth of the target microorganism) vs. bactericidal (killing cells)
  • Narrow spectrum (acting against a few specific bacteria) vs. broad spectrum (acting indiscriminately against many bacteria).

Clearly an ‘ideal’ antibiotic would be narrow spectrum and bactericidal, rapidly killing only the target bacteria. In contrast a broad spectrum, bacteriostatic antibiotic may only inhibit growth of the target bacterium and at the same time may be bactericidal to others.

And here we come to the basic problem of antibiotic use in general medicine. When a patient attends the doctor’s office with a complaint such as a sore throat or an ear infection, most likely due to a viral infection, the doctor has a few choices:

  1. The doctor can inform the patient that antibiotics would be ineffective, and that the infection will go away by itself in a few days, and that the patient go home, rest and take other remedies to target symptoms such as pain, fever, or congestion in the meantime.
  2. The doctor can succumb to pressure from the patient demanding a prescription ‘remedy’ and prescribe an unnecessary and useless course of antibiotics. While this was common in the past, in many countries doctors now stand firm, maintaining antibiotics would be ineffective and are not required.
  3. The doctor can offer a delayed antibiotic prescription – sending the patient away with a prescription but advising the patient to wait for a couple of days to see if symptoms resolve before deciding if the prescription is required. This approach is becoming more common and does reduce unnecessary antibiotic use.
  4. Finally, the doctor can determine that even if the original illness was caused by a virus, there is now a secondary bacterial infection and that a course of antibiotics is now required. The problem here is that without a laboratory test the doctor cannot be sure which bacterium is causing the disease so in order to be sure that the antibiotic will be effective, a broad spectrum antibiotic is often prescribed.

Any antibiotic prescription that the patient collects from the chemist (pharmacist) and starts taking, immediately causes collateral damage to their own resident microbiota. It is now well-established that a short course of antibiotics disrupts the gut bacterial community, killing many important resident bacteria. This can be observed by a reduction in diversity (see articles here and here, and figure here), meaning that fewer different bacterial groups can be detected. Normally once the patient stops taking the antibiotic the diversity of the community increases within a month, almost returning to the starting composition. Almost. Some bacterial species are particularly sensitive to certain antibiotics and may never recover. Oxalobacter formigenes, the bacterium that protects against kidney stone formation, is one example.

The other hidden effect of antibiotic treatment is that although all members of the microbial community may re-establish, they may not be the same as before. The levels of antibiotic resistance amongst bacteria isolated from samples from patients after seven days of antibiotic treatment were much higher than those from controls without any treatment, even four years later (see here). The selection pressure exerted on bacteria during short courses of antibiotic treatment results in transfer of antibiotic resistance genes, and the spread of resistance to many other members of the microbial community, increasing the overall resistance profile. Whilst this may not be immediately damaging to the health of the person, this change in baseline resistance does mean that a subsequent course of antibiotic treatment could be less successful because more bacteria will be able to withstand being affected by the antibiotic, and more bacteria will contain resistance genes that could be transferred to disease-causing bacterium.

Historically, as soon as we started using purified antimicrobials therapeutically, we started seeing rise of resistance to those antibiotics. The first recognised tetracycline resistance gene, otrA, was identified in Streptomyces, a genus of Gram-positive bacteria now known to produce many antimicrobial agents as secondary metabolites (see figure here).

The indiscriminate effects of antibiotics can be even more severe in hospitalised patients. Recurring Clostridioides difficile-associated diarrhoea (CDAD) is a direct consequence of antibiotic treatment. The microbial diversity decreases in patients receiving antibiotics for legitimate therapeutic reasons, and the Clostridioides difficile population expands to occupy empty niches. Overgrowth of C. difficile results in toxin production, abdominal pain, fever and ultimately CDAD. Treatment is difficult because some C. difficile strains are antibiotic resistant and C. difficile forms non-growing spores that persist during the antibiotic treatment. This means that even if the initial infection is successfully treated, once the antibiotic treatment ceases the spores can germinate and cause recurring C. difficile infections. Although initial treatment with antibiotics works for 75% of patients, the remaining 25% end up with recurring CDAD infections. A more effective treatment may be faecal microbial transplant (FMT) therapy (see blog post here).

Scientists have spent the last 20 years investigating the many ‘good microbes’ that inhabit our intestinal tracts leading to a much greater understanding of what they do, and the potential repercussions when we destroy them. This means we are now very aware of the collateral damage a course of antibiotics can have. A new era of developing the ‘good microbes’ themselves as therapeutic agents, using them to treat disease, or to recolonise damaged intestinal ecosystems, beckons. New drugs may take the form of next generation probiotics or whole microbial community faecal transplants, or even postbiotics, but the common feature is that they are derived from the abundance of our important natural gut inhabitants.

 

Probiotics: Money Well-Spent For Some Indications

/in featured, ISAPP Science Blog /by Mary Ellen Sanders

Eamonn M M Quigley MD, Houston Methodist Hospital and Weill Cornell Medical College, Houston, Texas, USA; Hania Szajewska MD, The Medical Univesrity of Warsaw, Department of Paediatrics, Poland; Dan Merenstein MD, Department of Family Medicine, Georgetown University

We read with interest and some concern the Medical News and Perspectives article by Jennifer Abbasi titled “Are Probiotics Money Down the Toilet? Or Worse?” (Abbasi 2019).  As researchers committed to the study of fecal microbiota transplant, prebiotics and probiotics, we find the title overly sensationalist for an article that ultimately provides a more nuanced view. It is unfortunate that the author focused on studies which either did not report on any clinical outcome and hence provide limited insight on the effectiveness of probiotics, or, whose null results likely reflect the late timing of the intervention while failing to refer to many high-quality studies that illustrate the subtlety of commensal and probiotic bacterial actions or clinical efficacy. Tanoue and colleagues provide a reminder that commensal engagement with the immune system is selective and precise (Tanoue et al. 2019). As Dr Knight points out, it would be surprising to witness the same response to any intervention in all individuals (Abbasi 2019). Efforts to individualize medical interventions, including probiotics, are worthwhile, but not yet realized. Until then, available evidence must be critically considered, but not ignored.  We wholeheartedly agree with the call for high quality clinical studies of probiotics but assert that it is also important to stress the challenges of performing clinical studies that seek to demonstrate clinical benefits in healthy human subjects; they require large study populations and are consequently very expensive. That clinical studies have been performed and demonstrated robust and clinically meaningful outcomes was illustrated by the study of Panigrahi where they demonstrated that an intervention comprising a probiotic plus prebiotic reduced sepsis among high-risk infants in rural India (Panigrahi et al. 2017). In the meantime, meta-analyses of smaller studies can provide insights into clinical benefit or harm. For example, systematic reviews and meta-analyses have consistently supported a role for probiotics in the prevention of Clostridium difficile–related illness, leading a JAMA review to state: “moderate-quality evidence suggests that probiotics are associated with a lower risk of C. difficile infection” (Goldenberg et al. 2018). Balanced with the low number needed to harm, probiotic interventions are attractive clinical options. We also question Abbasi’s focus on colonization as there is little, if any, evidence that this is necessary for probiotic activity.

We stress the obligation to provide a balanced view of the field which provides equal emphasis on successes as well as failures. No two probiotics (or probiotic cocktails) are alike; we should not expect they all have the same clinical impact.

 

References

  1. Abbasi J. Are probiotics money down the toilet? Or worse. JAMA 321(7):633-635. doi:10.1001/jama.2018.20798
  2. Tanoue T, Morita S, Plichta DR, et al. A defined commensal consortium elicits CD8 T cells and anti-cancer immunity. Nature. 2019;565:600-605.
  3. Panigrahi P, Parida S, Nanda NC, et al. A randomized synbiotic trial to prevent sepsis among infants in rural India. Nature. 2017;548:407-412.
  4. Goldenberg JZ, Mertz D, Johnston BC. Probiotics to prevent Clostridium difficile infection in patients receiving antibiotics. JAMA 2018;320:499-450. 

 

Acknowledgements:

Conflicts of interest:

All three authors are members of the Board of Directors of ISAPP

Eamonn M M Quigley holds equity in Alimentary Health and has served as a consultant to Alimentary Health, Allergan, Axon Pharma, Biocodex, Glycyx, Menarini, Pharmasierra, Salix and Vibrant.

Hania Szajewska reports no conflicts

Dan Merenstein has served as a consultant to Bayer, Debevoise & Plimpton, Pharmavite and Reckitt Benckiser

hospital_room

Late initiation of probiotic therapy for acute pediatric gastroenteritis may account for null results

/in featured, ISAPP Science Blog, News /by Mary Ellen Sanders

Francisco Guarner, MD, PhD, University Hospital Vall d’Hebron, Barcelona, Spain; Michael Cabana, MD, MPH, University of California, San Francisco, CA, USA; and Mary Ellen Sanders, PhD, International Scientific Association for Probiotics and Prebiotics, Centennial, CO, USA. 

Schnadower et al (1) and Freedman et al (2) conclude that probiotics given to children who presented to emergency departments with gastroenteritis are not effective; however, these new well-conducted trials used probiotics in children who were symptomatic much longer than when current recommendations suggest initiating therapy.  Both studies recruited children that were symptomatic for up to 72 hours or more at time of randomization. Half the cohort of Freedman (2) had diarrhea for 43 hours at randomization. In the study by Schnadower, (1) children were symptomatic at randomization for a median of 53 hours. It is not surprising that probiotic intervention at this late stage was not successful, since most children were close to spontaneous remission. Acute gastroenteritis in high-income countries is usually benign and after 48 hours typically remits spontaneously. These new studies should not change current recommendations (3,4,5) to use probiotics early after onset of pediatric gastroenteritis in conjunction with oral rehydration, consistent with previous beneficial trials.

 

  1. Schnadower D, Tarr PI, Casper TC, et al. Lactobacillus rhamnosus GG versus placebo for acute gastroenteritis in children. N Engl J Med. 2018; 379(21):2002-2014.
  2. Freedman SB, Williamson-Urquhart S, Farion KJ, et al. Multicenter trial of a combination probiotic for children with gastroenteritis. N Engl J Med. 2018;379(21):2015-2026.
  3. Allen SJ, Martinez EG, Gregorio GV, Dans LF. Probiotics for treating acute infectious diarrhoea. Cochrane Database Syst Rev. 2010 Nov 10;(11):CD003048.
  4. Szajewska H, Guarino A, Hojsak I, et al. Use of probiotics for management of acute gastroenteritis: a position paper by the ESPGHAN Working Group for Probiotics and Prebiotics. J Pediatr Gastroenterol Nutr. 2014;58(4):531-9.
  5. Lo Vecchio A, Dias JA, Berkley JA, et al. Comparison of recommendations in clinical practice guidelines for acute gastroenteritis in children. J Pediatr Gastroenterol Nutr. 2016;63(2):226-35.

 

ISAPP-initiated systematic review and meta-analysis shows the association of probiotic consumption with reduced antibiotic prescriptions

/in featured, ISAPP Science Blog, News /by Mary Ellen Sanders

At the ISAPP meeting in Turku, Finland in 2016, scientists convened a working group led by Dan Merenstein of Georgetown University (USA) along with Irene Lenoir-Wijnkoop of University of Utrecht (the Netherlands) and Danone Research. In their discussions, the group identified a gap in the literature: a systematic review of randomized, controlled trials to determine how antibiotic prescriptions are associated with probiotic consumption for the prevention of common acute infections. The protocol was registered with PROSPERO (registration number CRD42016052694).

The analysis, authored by ten scientists, was recently published—and results showed that infants and children who received probiotics were at least 29% less likely to be prescribed antibiotics. Find the paper here in the European Journal of Public Health.

ISAPP scientists say probiotics deserve consideration as a public health intervention that may reduce the widespread over-prescription of antibiotics.

See the ISAPP press release here, and the Georgetown University press release here.

See here for media coverage of this paper:

http://www.microbiometimes.com/scientific-analysis-shows-probiotic-use-is-associated-with-fewer-antibiotic-/

https://www.pharmacytimes.com/resource-centers/vitamins-supplements/daily-probiotics-may-reduce-kids-need-for-antibiotics

https://www.news-medical.net/news/20180914/Probiotics-could-reduce-the-need-for-antibiotics.aspx

Clinical evidence and not microbiota outcomes drive value of probiotics

/in featured, News /by Mary Ellen Sanders

By ISAPP Board of Directors, plus Prof. Francisco Guarner and Dr. Bruno Pot

September 10, 2018

Two recent papers have generated much adverse publicity for the probiotic field. Headlines driven by sensationalism, not data, claim “Probiotics labelled ‘quite useless’” (BBC) and “Probiotics ‘not as beneficial for gut health as previously thought’” (The Guardian). The quotes are from author Eran Elinav, who generalizes the study findings to all ‘probiotics’ as a class – a generalization that ignores that specific probiotic are meant for specific purposes. This research was published this month in Cell (here and here).

The scope of these papers is limited to microbiome data; no clinical endpoints are assessed. Without clinical evidence, it is not possible to conclude about the tested probiotic’s usefulness, and it is certainly not possible to conclude about probiotic usefulness in general. Stating that probiotics are ‘quite useless’ or ‘not as beneficial’ is, quite simply, wild and factually inaccurate. The authors discount the existing body of evidence for probiotic health benefits, including Level 1 placebo-controlled, randomized trials. Cochrane reviews (the gold standard used by physicians and public health policy makers) of the totality of evidence show that specific probiotics can prevent antibiotic associated diarrhea (AAD) and C. difficile diarrhea. This evidence has been translated into evidence-based recommendations for probiotics issued by medical groups. Regardless of an effect on the microbiota, these are established, evidence-based benefits of probiotics.

No clinical endpoints tracked in either study

What these papers provide is extensive data about the impact of one product containing 11 common probiotic species on different microbiome measures. To the authors’ credit, they analyzed mucosal and luminal samples from humans, in addition to samples from stool.  Nonetheless, the probiotic definition [live microorganisms that, when administered in adequate amounts, confers a health benefit on the host (Hill et al 2014)] does not require that probiotics function via interaction with the microbiota, nor is there much evidence that they alter the microbiota composition in an appreciable manner. Absence of impact on microbiome measures is not evidence that probiotics lack clinical or physiological effects. Probiotics function via many mechanisms that might not be revealed by the measures made in these papers.

Methodological concerns

A careful reading of this paper reveals many methodological concerns.

The extensive data in the paper is an assortment of different types of analyses. For example, for a beta-diversity metric, they sometimes use weighted Unifrac, sometimes unweighted Unifrac, and sometimes Bray-Curtis, without an explanation for their choice. These approaches to presenting the data can give very different results. With the transcriptomics data, sometimes the authors choose samples from the duodenum and sometimes the jejunum. For example, in figure 6, panels C-E compare the difference in gene expression between the naïve group and the treatment in the duodenum, whereas in panels F-H they compare the antibiotic state with the treatment in the jejunum. Such an approach leads the reader to speculate that the authors picked the metrics and data that best fitted the story they wanted to tell. In a well-conducted clinical trial, the statistical plan is registered before the study starts, to assure readers that the scientific process of advancing a hypothesis and designing a study to test the hypothesis is respected.

The probiotic was not administered to human subjects until 7 days after the treatment with antibiotics commenced, after the damage by the antibiotics has been done. Dozens of human studies with specific probiotics have documented that probiotics prevent AAD or C. difficile infection. In most clinical trials, the probiotic is administered together with the antibiotics. A recent meta-analysis concluded that “administration of probiotics closer to the first dose of antibiotic reduces the risk of (Clostridium difficile infection) by >50% in hospitalized adults.” (Emphasis added) The approach in the Suez et al paper is not consistent with the aforementioned clinical studies, with how probiotics are used in clinical practice or with the knowledge of how probiotics most likely prevent AAD. When provided on the same days as antibiotics, probiotics have the opportunity to prevent overgrowth of opportunistic, antibiotic-resistant microbes by competitive exclusion in the ecosystem. Therefore, the microbiome findings of Suez et al likely cannot be applied to clinical trials with such different time course of antibiotic/probiotic administration.

Several conclusions about the effect of probiotics on the microbiota were based on relative abundance measures, which do not relate to actual bacterial numbers or metabolic activity of all relevant species in the gut.

The antibiotic treatment used was potent for a study population that would otherwise not need antibiotics. Volunteers were administered oral ciprofloxacin 500 mg bi-daily and oral metronidazole 500 mg tri-daily for a period of 7 days. They are both very strong and indiscriminate antibiotics, having a severe impact on the gut microbiota.  One could question if this drug therapy might have a different impact on the microbiome of a healthy person compared to a patient likely to receive this treatment, i.e., one whose microbiota ecosystem is disrupted by disease or fever.

The probiotic product

A serious issue is that the authors chose a product for this study that has no demonstrated clinical benefits. At a minimum, the product used for this study should have evidence for impact on antibiotic associated conditions, including symptoms or emergence of opportunistic pathogens. The 3 (possibly 2, as the latter 2 appear to be the publication of the same data) human studies conducted on this product (here, here and here), showed no clinical benefit. Thus, the investigators tested the potential benefits of a product for which no benefits had been previously shown. Further, the papers do not adequately describe the product; only a total count (25 billion) is given; counts of each strain – through the end of the administration period – should have been provided. Furthermore, the authors state about the product that “B. longum was probably represented by two strains.” This constitutes imprecise characterization unacceptable in a well-defined probiotic product.

Appearance of author bias

The conclusions reached in the papers promote a personalized approach to probiotic use. In an article on the BBC, the lead author stated, “In the future probiotics will need to be tailored to the needs of individual patients. And in that sense just buying probiotics at the supermarket without any tailoring, without any adjustment to the host, at least in part of the population, is quite useless.” The authors did not disclose they are involved with a company promoting this personalized approach.

Probiotic colonization

The authors suggest that their finding that probiotics do not colonize long term is noteworthy. In fact, researchers in this field have known this for 30 years: most probiotics do not colonize or become established as part of the resident microbiota. A 2016 paper by Madonado-Gomez et al was notable precisely because a Bifidobacterium longum strain was found that did persist. In most cases, probiotic effects are likely mediated by transient effects.

Responders and non-responders

A well-established concept in medicine is that some people respond clinically and physiologically to interventions and others don’t. This is the case with much of probiotic as well as pharmaceutical literature. (See review on responders and non-responders to probiotics by Reid et al.) An individual’s response is likely impacted by diet, resident microbes, host genes and host physiology/health. The validity of a personalized approach to probiotic administration remains to be determined, as evidence for a clinical benefit to the approach is needed. Microbiome data alone are not sufficient.

Need for future research

In the Cell publications, the authors acknowledge their study was limited due to lack of clinical endpoints and the testing of only a single product. It is unfortunate that the press marched ahead with inflammatory stories about the negative effects of probiotics based on such paltry evidence. The scientific community understands that this is one study, on a small number of human subjects, by one research group. Sweeping conclusions cannot be made. There are many hypotheses that can be generated from this study that can lead to follow up studies, which we hope will ensue.

Conclusions

Hundreds of human trials have demonstrated clinical benefits of probiotics and several evidence-based recommendations have been issued by medical organizations. Of course, not all studies are positive. Not all probiotics work for all conditions. But the safety record of probiotics administered to healthy as well as many patient populations is well-established. Numerous media outlets have reported on these two studies as if they are proof that probiotics are useless at best and harmful at worst. This irresponsible reporting may lead people who are benefitting from probiotics to stop using them, potentially causing real harm.

The erroneous interpretation of the current study and previous research by the primary author is disingenuous, as he states,  “Contrary to the current dogma that probiotics are harmless and benefit everyone, these results reveal a new potential adverse side effect of probiotic use with antibiotics that might even bring long-term consequences.” This comment and the papers’ conclusions are not corroborated by the totality of safety and efficacy clinical evidence on probiotics, which includes thousands of probiotic-treated subjects. In comparison, the data in Suez et al come from microbiome assessments from only eight probiotic-treated subjects.

Furthermore, this paper evaluated just one product of limited provenance and containing a combination of multiple, incompletely characterized strains. This is in sharp contrast to numerous studies of precisely characterized strains demonstrating well-defined and beneficial engagements with the host. Zmora and colleagues and Suez and colleagues are to be congratulated on their attempts to characterize in detail the impact of one probiotic product on a perturbed, human microbiome. We look forward to further such studies employing well-characterized strains with demonstrated clinical benefits and including relevant clinical endpoints.

Additional reading:

Risk assessment of probiotics use requires clinical parameters

ISAPP comments: International Group of Probiotic Scientists Weighs in on Flawed Conclusions From New Scientific Papers

American Gastroenterological Association response: AGA’s Interpretation of the Latest Probiotics Research

Response by Prof. Gregor Reid:  Trying to Close the Stable Door After the Horse Has Bolted

cber

CBER to hold public workshop on regulation of biologics

/in featured, News /by Mary Ellen Sanders

FDA’s Center for Biologics Evaluation and Research (CBER) is convening a public workshop Sept 17 in Rockville MD on the Science & Regulation of Live Microbiome-Based Products Used to Prevent, Treat, or Cure Diseases in Humans. It is now open for registration (free). See here for the program and here for additional info.

The evidence for efficacy, the safety and the regulatory framework for probiotics other live microbiome based products will be discussed. Prof. Dan Merenstein MD, ISAPP’s current Vice President, will speak on evidence, research and clinical use of probiotics for antibiotic associated diarrhea. Although the title suggests the meeting will focus on drugs, Dr. Bob Durkin from the Center for Food Safety and Applied Nutrition (CFSAN) of the FDA will speak on probiotic foods and dietary supplements.

This workshop is an opportunity for stakeholders to share with FDA and NIH concerns regarding the regulatory approach to probiotics adopted by the FDA. The path for development of probiotic drugs is reasonably clear. But the road to develop probiotic foods, supplements or microbiome-based dietary strategies to compensate for deficient microbiota is less so. These products are intended to improve gut function, nutritional status, immune status, metabolic properties and more. These are legal functions for foods and supplements, but the FDA doesn’t seem to see it that way.

The FDA has for the most part has approached probiotics as drugs (Sanders et al. 2016). Since probiotics are live microbes, and since CBER deals with drugs that are derived from living sources, CBER often oversees human research on probiotics. But there is no mechanism within CBER to oversee foods and supplements, and hence, human research on probiotics tends to be shunted into the investigational new drug (IND) process. But, the legal definitions of drugs and foods overlap – both can impact the structure/function of the human body and both can reduce the risk of disease. So conducting such research on probiotic foods – and not as part of the IND rubric – should be possible. Perhaps progress on this front can be achieved in the CBER workshop in September.

In a press announcement, FDA Commissioner Scott Gottlieb MD shared FDA perspective on probiotics and promoted this CBER conference. A couple of issues are noteworthy in this announcement by Gottlieb. First, the term ‘probiotic’ is used. Over the years, the FDA largely avoided use of this term, instead favoring the term live biotherapeutic product (LBP). But these terms are not synonymous. Probiotic is defined as a live microorganisms that, when administered in adequate amounts, confers a health benefit on the host (Hill et al. 2014). It spans multiple regulatory categories. A LBP is by definition a drug. The fact that Gottlieb used the term ‘probiotic’ may signal that he recognizes that not all probiotics are drugs. Second, Gottlieb’s announcement shows awareness that probiotics are legitimate components in foods and dietary supplements and states that the FDA is “committed to working with industry on efforts to provide information that can help consumers make more informed choices about these products.” This is a welcome statement to many researchers involved in probiotic foods and supplements in the United States. It suggests that the FDA is willing to look beyond probiotics as LBPs and develop regulatory approaches for research and claims appropriate to foods and supplements.

Innovation in this field, which has the potential to benefit many people globally, requires regulatory approaches that do not obstruct. Participation in this workshop may lead to improvements that both protect public safety and facilitate academic and industry researchers in the United States on the path to discovery.

 

Additional information:

Sanders ME, Shane AL, Merenstein DJ. Advancing Probiotic Research in Humans the United States: Challenges and strategies. Gut Microbes 7(2):97-100.

Warning letter from CBER: Dietary Supplements Containing Live Bacteria or Yeast in Immunocompromised Persons: Warning – Risk of Invasive Fungal Disease. Posted 12/09/2014.

probiotics association of india

ISAPP Goes to India

/in featured, ISAPP Science Blog /by Mary Ellen Sanders

By Mary Ellen Sanders PhD and Dan Merenstein MD

ISAPP sent two key-note speakers to the Probiotics Association of India meeting, held Feb 16-17 in New Delhi. Prof. Dan Merenstein MD spoke on “Evidence for clinical indications: how do probiotics measure up?” and Dr. Mary Ellen Sanders addressed “Is it time for live cultures to be included in official dietary recommendations?”  Dr. Merenstein also gave a second talk on an ISAPP-supported project:  the evidence that probiotic consumption can reduce antibiotic utilization. This is the 3rd PAi meeting that ISAPP has supported through speaker sponsorship.

The meeting featured talks on synbiotics to prevent late-term sepsis (Pinaki Panigrahi), the impact of diet on the Indian gut microbiome (Yogesh Shouche), autism (Sheffali Gulati) and 10 selected student/young investigator presentations on diverse microbiota/probiotic studies. Because of the high quality student presentations, judges were unable to choose the best to award prizes. The solution: all 10 presentations were awarded 5000 INR, supported by Prof. Pinaki Panigrahi’s Center for Global Health and Development. A poster session and original probiotic-themed drawings (see below for one submission) were also presented.

Dr. Sanders also spoke on “The contribution of probiotics to health” in an event held February 15 sponsored by the Gut Microbiota and Probiotic Science Foundation (India). This event was attended by ~150 professionals in nutrition, medicine and microbiota/probiotic research.

Of course, the trip was not all work. Below, Mary Ellen takes a selfie with her new elephant friend, Sampa.

probiotic poster

Probiotics and Good Gut Health. An artistic interpretation by a student, Simranjeet Singh.

elephant india

Mary Ellen Sanders takes selfie with Sampa, a 62-year old Asian elephant.

news probiotics UK

ISAPP works to have evidence-based usage of probiotics to prevent antibiotic-associated diarrheoa implemented in UK

/in featured, News /by Mary Ellen Sanders

January 12, 2018. Antibiotics are amongst the most commonly prescribed drugs in UK hospitals. However, as well as treating infection they can cause disruption to the gastrointestinal microbiota. This can lead to the relatively common side-effect of antibiotic-associated diarrhoea (AAD) which often delays discharge. More concerning is that a disruption to the normal gut microbiota can lead to reduced resistance to opportunistic pathogens such as Clostridium difficile, leading to C. difficile infection, a potentially severe or fatal infection. Based on the available evidence, probiotics are a safe and effective adjunct to antibiotics to reduce the risk of developing AAD and for the primary prevention of CDAD. The International Scientific Association of Prebiotics and Probiotics has reviewed available data and supports several published assessments, which recommend probiotics as adjunctive therapy for prevention of AAD and CDAD.

This effort was led by Dr. Claire Merrifield BSc MBBS PhD, Speciality Registrar in General Practice, St. Mary’s Hospital, Imperial College Healthcare Trust, Imperial College London and Prof. Daniel Merenstein, MD, Department of Family Medicine, Georgetown University Medical Center and ISAPP Board Member and Treasurer.

Read full recommendation here, which will be sent to NICE and Public Health England.

watch with times they are a-changin quote by bob dylan

The Times They Are A-Changin’ With Probiotics

/in featured, ISAPP Science Blog /by Mary Ellen Sanders

December 15, 2017. By Prof. Daniel Merenstein, MD, Department of Family Medicine, Georgetown University Medical Center, Washington DC.

I had a surprising encounter a few weeks ago in the clinic. I was caught off guard, had to take a step back and think about what happened. I recommended to my patient that she take a probiotic with the antibiotic I was prescribing. She said to me, “What is a probiotic?” My response was, “A probiotic,” as if it didn’t require any further explanation. It was nearly incomprehensible to me that she didn’t know what a probiotic was and maybe she just didn’t hear me or just didn’t understand me (I tend to speak too fast). But no, she just didn’t know what one was. I then realized how unusual this encounter was.

Something has been a-changing. It hasn’t been a quick process and I am not sure when it changed, but it did. Even just a few years ago when I recommended supplementing a course of antibiotics with a probiotic, people were generally receptive and had a vague idea about probiotics. However we generally had to talk about what probiotics were and how to use them. Fast forward to today and it appears to me that 95% of people respond, “I already take one.” Much more common than hearing “What’s a probiotic?” is to hear, “Of course, you always have to take a probiotic when taking an antibiotic.”

I am currently recruiting for my 8th probiotic clinical trial (PLAY ON). My team has recruited over 1,400 participants for previous studies. We have a system and a great team, but we are having the most difficult time recruiting for this study. I have thought a lot about why and I think it comes down to the times they are a-changin’. When we started on this research path 12 years ago, our research team and the subjects we recruited were excited about probiotics and their potential. But today the public doesn’t see the potential of probiotics; they know probiotics impact the gastrointestinal tract and should be used when taking antibiotics. Therein lies our challenge: to be in our study a subject has to be willing to take the chance of being in the placebo group. That makes little sense to a public that already knows to take a probiotic when on antibiotics.

My first two NIH studies were funded by the National Center for Complementary and Integrative Health, while my current study is funded by the National Institute of Child Health and Human Development. The shift has occurred from complementary, to mainstream. One need no longer attend a microbiome or probiotic conference to hear talks on probiotics; nearly all clinical conferences will now have probiotic talks. I am confident my team will adjust to these changing times but I think more important is how researchers and clinicians adjust. Probiotics are not alternative options anymore, the evidence base is robust and some indications well-studied. The discussions need to shift from, “You should have probiotics on formulary” to specific recommendations of which probiotics should be used for what indications. Similarly when discussing other disease states in the gut (e.g. necrotizing enterocolitis, infantile colic, and irritable bowel syndrome), it is time to take the next step and discuss specific recommendations. I am sure I will see another patient who has never heard of probiotics, but I’m willing to bet that doesn’t happen for many months. More likely, I expect I will be discussing the efficacy of the products my patients are already taking. That is an important change that docs need to think about.

Come gather ’round people
Wherever you roam
And admit that the waters
Around you have grown
And accept it that soon
You’ll be drenched to the bone.
If your time to you
Is worth savin’
Then you better start swimmin’
Or you’ll sink like a stone
For the times they are a-changin’.

Bob Dylan, Nobel Laureate

The Times They Are A-Changin’

Columbia Records, 1964

probiotics for healthy people infographic

ISAPP releases new infographic: “Probiotics for Healthy People”

/in featured, News /by Mary Ellen Sanders

November 20, 2017. Probiotics are most commonly studied with for populations with a specific condition—frequent examples include diarrhea, irritable bowel syndrome, and pouchitis. But what kind of evidence exists on probiotics for healthy people?

A new ISAPP infographic gives an overview of what we know about the use of probiotics in healthy individuals. The resource was developed by ISAPP’s Science Translation Committee and approved by  the ISAPP board of directors.

“Studying health benefits in healthy people is a challenge. But there is evidence that probiotics can provide dietary management of some digestive conditions that don’t reach the level of diagnosed disease as well as prevent of some common infectious diseases and. These, and other benefits, are of value to healthy people,” says ISAPP’s Executive Science Officer, Dr. Mary Ellen Sanders. The new infographic  emphasizes it is not necessary to take probiotics to be in good health, but they may serve as a useful addition to a healthy lifestyle.

Research investigating how probiotics can affect healthy individuals through their microbiomes is ongoing in laboratories around the world, and ISAPP continues to track the latest findings.