Difficulty in falling asleep or in staying asleep, waking up early... insomnia affects one in two adults over 65 years of age. With serious consequences for health since this chronic disorder is often accompanied by cognitive decline and increased mortality. Although the mechanisms are still poorly understood, an explanation of the link between insomnia and cognitive decline could lie in the gut microbiota-brain axis. A team of researchers therefore studied the links between the gut microbiota and the cognitive performance of 72 chronic insomniacs (of which 56 were women) with an average age of 73.2 years. Two factors were assessed, which generally testify to an accelerated cognitive decline during aging: sleep quality (objective measurement by actigraphy (sidenote: Actigraphy Objective method of measuring sleep based on a device similar to a watch, worn on the wrist or ankle, which detects movements of the body and therefore waking activity. This apparatus thus measures the time taken to fall asleep, any periods of wakefulness and their duration, etc. ) over 2 weeks and subjective measurement by self-questionnaire) and cognitive performance (15 variables measured including 2 finally retained as being more discriminating).

Sleep quality associated with intestinal dysbiosis

Analysis of stool samples of patients by sequencing of the 16S rRNA gene demonstrates the presence of 45 different phyla. Bacteroidetes were predominant (48%), followed by Firmicutes and, a long way behind, Proteobacteria (6 %), that is a decrease in Firmicutes and Proteobacteria in favor of the Bacteroidetes in comparison with patients without sleep problems².

But above all, in the 72 insomniacs monitored, sleep efficacy (that is objective sleep not perceived sleep) and cognition explained 7.5 to 7.9% of the total variation in the composition of the gut microbiota (in terms of bacterial variants and genera (sidenote: Amplicon Sequence Variant (ASV) Term designating individual DNA sequences recovered from a marker gene analysis (“parasite” sequences induced by gene amplification and sequencing are eliminated by this technique). This method is therefore distinguished from OTU counts, (Operational Taxonomic Unit), more commonly used, where bacteria are grouped together based on similarities of a given gene serving as a taxonomic marker. ) ). That is a significant impact, comparable to that caused by medicines, blood parameters, intestinal transit, diet, state of health, and anthropometric data, according to a previous study³.

Lachnoclostridium and Blautia involved?

In addition, the correlation analysis showed that a strong presence of the genus Lachnoclostridium went together with effective sleep and higher cognitive performance (shorter response time). Conversely, decreased cognitive performance was associated with greater abundance of the genus Blautia.
This study provides a new building block in the relationship between insomnia, cognition, and the gut microbiota. Although it does not allow any causality to be inferred, it points the finger at the gut microbiota as a potential aid to the diagnosis of elderly persons suffering from sleep disorders and cognitive decline, even as a new therapeutic target in the field of aging.

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What is exactly the vaginal microbiota and what is its role?

Prof. Ina Schuppe Koistinen: The vaginal microbiota is defined as the complex ecosystem of microorganisms (sidenote: Microorganisms Living organisms too small to see with the naked eye. This includes bacteria, viruses, fungi, archaea, protozoa, etc., collectively known as ’microbes’. Source: What is microbiology? Microbiology Society. ) , including bacteria, virus and fungi, that live inside the vagina and has biologically evolved to help protect the female reproductive system. 

Unlike in the gut, a healthy vaginal microbiota has low diversity and is dominated by Lactobacillus species. Lactobacilli protect the vagina from overgrowth of other organisms by keeping the vaginal pH low by production of lactic acid, production of antimicrobials such as H₂O₂ and bacteriocins. They also compete for nutrients, adhere tightly to the mucosal membrane and modulate the local immune system.

How does the vaginal microbiota change during the menstrual cycle? 

I. S.-K.: We know that a healthy vaginal microbiota is resilient to changes such as menstruations, sexual activities and hormonal fluctuations. For most but not all women, the vaginal microbiota remains relatively stable during periods. Menstrual blood, increases pH and adds nutrients to vaginal bacteria like Gardnerella or Prevotella that are associated to an unbalanced vaginal microbiota (what we call a dysbiosis (sidenote: Dysbiosis Generally defined as an alteration in the composition and function of the microbiota caused by a combination of environmental and individual-specific factors. Levy M, Kolodziejczyk AA, Thaiss CA, et al. Dysbiosis and the immune system. Nat Rev Immunol. 2017;17(4):219-232.   ) ).

So, there is an effect during bleeding when the vaginal microbiota gets more diverse¹ but normally, it will recover when the menstrual phase is over (that’s what we call “resilience”).

Do hygienic protections impact my vaginal microbiota?

I. S.-K.: There is little scientific data on the link between menstruation, hygienic protection method and the vaginal microbiota. We don’t know at this point if hygienic protections influence it’s composition. It is truly critical because half of the female population (around 26% of the global population²) are of reproductive age and concerned, but no large cohort studies have already compared different hygienic protections: tampon, pad, menstrual cup or absorbent pantie. In an ongoing research study, in Sweden we investigate the impact of hygienic protection on the vaginal microbiota of 2000 women. I can’t wait to see the results.

Is there a link between painful periods and microbiota?

I. S.-K.: Once again, unfortunately there is very little research on that topic. In a study from Sweden³, 50% of adolescent girls reported pain during their periods, almost 40% severe pain. Research has shown that women with period pain have high levels of prostaglandins, hormones known to cause cramping abdominal pain.

At this point, we don’t know if the microbiota is involved. We have to enhance research because girls have always been told that it is normal to have period pain. But it is not normal! We have to investigate factors associated with menstrual pain to relieve women and improve the diagnosis of endometriosis. According to Forbes, only 4% of all R&D funding in Pharma is dedicated to specific women’s health issues which is quite discouraging… I’m convinced that we need to raise awareness on this topic, it’s my mission!

Is there any risk of increased vaginal infections during the menstrual cycle? Is it linked to my microbiota? 

I. S.-K.: The risk of vaginal infections (Candida infections or bacterial vaginosis) increases during periods and this is linked to the vaginal microbiota. As I have already explained, the menstrual blood creates an environment that favors the growth of pathogenic bacteria, leading to dysbiosis (sidenote: Dysbiosis Generally defined as an alteration in the composition and function of the microbiota caused by a combination of environmental and individual-specific factors. Levy M, Kolodziejczyk AA, Thaiss CA, et al. Dysbiosis and the immune system. Nat Rev Immunol. 2017;17(4):219-232.   ) .

According to Water Aid (sidenote: Sources ) , 72 million women around the world have to manage their periods without a decent toilet. In addition, women may not be able to afford hygiene protection and are at increased risk for infections. Both resources and education are needed to improve the situation.

Sex during periods: does it have an impact on the vaginal microbiota and the risk of infections?

I. S.-K.: Having sex during periods is totally fine, but if your vaginal microbiota is more susceptible to dysbiosis, the use of condoms is recommended. All sex practices where body fluids are exchanged can worsen the vaginal dysbiosis. A dysbiotic vaginal microbiota makes you more susceptible to sexually transmitted infections by bacteria, such as chlamydia and gonorrhea, and viruses, such as human papillomavirus (HPV) or HIV^4-6. 

Any advice on how to take care of your vaginal microbiota during periods? 

I. S.-K.: The first advice I will give is that every woman should choose the product she is comfortable with. It will help her to manage her periods in a good way, to feel comfortable and safe. It is important to choose a product that matches your blood flow.

Then, there are very simple rules to follow: change your tampon or your menstrual cup (you need to sterilize it before insertion) every 4-6 hours to limit the risk for toxic-shock syndrome (sidenote: Toxic-shock syndrome This is a rare but life-threatening condition caused by bacteria getting into the body and releasing harmful toxins, and associated with tampon and or cup use. Sources. ) ⁷. Wash your hands before inserting your hygienic protection, avoid tampons or pads with perfume and other kinds of chemicals. Your vagina cleans itself with its own discharge, there is no need for vaginal douching. Wash your vulva with lukewarm water, a soap-free cleaning solution or perfume free oils and do not use antimicrobials that can disturb your microbiota. Practice safe sex and be nice to your vulva and vagina, not too much soap and perfume, that is the best advice I can give!

Discover Prof. Ina Schuppe Koistinen's interview:

BMI 22.55

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Urethritis is an inflammation of the urethra (sidenote: Urethra The tube that carries urine from the bladder and out of the person’s body. ) , the tube through which urine leaves the bladder. In men, it manifests as a burning sensation on urination, with itching and abnormal discharge. It can be caused by a sexually transmitted infection (STI) triggered by a bacterium, usually Neisseria gonorrhoeae (gonococcus), and sometimes Chlamydia trachomatis or Mycoplasma genitalium, or less commonly by viruses such as herpes. However, up to half of cases of non-gonococcal urethritis are considered “idiopathic,” meaning we do not know what caused them. Either the urethritis is not infectious, which is rare, or the pathogen responsible is not identified. If in doubt, doctors usually prescribe an antibiotic. But this type of non-targeted approach can result in inadequate or excessive treatment, which can in turn alter the microbiota.

Close-up on the urethral microbiota of men with idiopathic urethritis

Recent studies also suggest that the infectious agents responsible for non-gonococcal urethritis in men who have sex with women (MSW) are not the same as in those who have sex with men (MSM). Australian researchers therefore sought to determine which bacteria, apart from those already known, might contribute to infection in humans, taking into account their sexual practices. To do so, they analyzed the urethral and urinary microbiota of around one hundred men (MSW and MSM) with symptoms of idiopathic urethritis and compared them to around one hundred men without urethritis, as “control” subjects.

(Bacterial) genus and sexual orientation issues

Scientists found that the bacterium Haemophilus influenzae, which naturally colonizes the microbiota of the nasopharynx (in other words, the nose and throat), was more abundant in the urethral microbiota of MSM with idiopathic urethritis. The researchers believe that this infection may be transmitted by the act of having oral sex without a condom. The scientists found more of the bacterial genus Corynebacterium in affected MSW, which was surprising because it is considered normal in male genital microbiota. The authors suggest that some of these species may become pathogenic on multiplying. Other bacterial genera such as Ureaplasma, Escherichia, some streptococci and a staphylococcus were also more abundant in the urinary and urethral microbiota of the affected men. The scientists believe they may also promote urethritis.

Hope for more targeted treatments for male urethritis

The discovery of these new bacteria brings hope for patients. Thanks to these new bacteria, researchers can now identify possible causes of non-gonococcal infectious urethritis based on the sexual orientation of patients. If these results are confirmed, doctors could offer their patients more targeted treatments. A small step for science, a giant leap for sexually transmitted infections (STIs)?

Faced with COVID-19, pregnant women present an increased risk of developing a severe form and pregnancy complications, such as preeclampsia or premature birth. Well, the role played by a balanced vaginal microbiota in the optimal progression of pregnancy is known. And what if the harmful effects of COVID-19 in pregnant women required the intervention of the vaginal microbiota?
In order to check this hypothesis, researchers conducted a prospective case-control study including 28 non-infected pregnant women and 19 pregnant women suffering from COVID-19 (13 mild or even asymptomatic cases and 6 moderate to severe cases, including 2 that required the taking of antibiotics and antivirals).

More diversity and fewer lactobacilli among the COVID-19 pregnancies

A sample of the vaginal microbiota was obtained with a swab during the active phase of the disease in the month following recovery and evaluated by 16S rRNA gene sequencing. The COVID-19 group displayed significantly greater diversity than the control group. In addition, the Bacteroidetes had gained the upper hand over the Firmicutes, and, at bacterial genus level, the Lactobacillus sp. were significantly less abundant than in the control group. Well, previous studies showed that there was an increased risk of miscarriage or premature birth in pregnant women whose vaginal microbiota were depleted in Lactobacilli. These data corroborate this finding, since 3 women in the COVID-19 group gave birth prematurely (versus 0 in the control group).

Is the severity of COVID-19 related to vaginal dysbiosis?

Despite the small size of the sample, the investigators observed other differences in the composition of the vaginal microbiota in the COVID-19 group. In particular, the women suffering from moderate to severe forms of COVID-19 displayed much higher levels of Ureaplasma spp.: 2.05% vs 0.1% in case of asymptomatic to mild forms. The genus Ureaplasma is involved in different gynecological infections (salpingitis, urethritis, and cervicitis), its over-representation in case of severe COVID-19 also argues in favor of an association of vaginal dysbiosis both with SARS-Cov-2 infection and risks of pregnancy complications. All the more as, in the 3 premature births that occurred in this study, 2 were in the moderate to severe COVID-19 subgroup (n=6).

Synopsis of the course

In recent years, probiotics have gained enormous scientific relevance, as there has been an increasing number of studies supporting probiotic health benefits beyond the digestive tract, including oral, liver, skin, vaginal and urinary tract health. However, not all probiotics are the same. The decision of choosing a probiotic should be based on clinical recommendations based on their efficacy to treat certain pathologies. Among a wide variety of probiotic products, how to choose one? And why? This course will give you the clues and rationale behind selecting a probiotic. Moreover, do not miss the opportunity of learning from a renowned expert some misconceptions and practical recommendations regarding probiotics use!
 

Who is Mary Ellen Sanders?

• Mary Ellen Sanders, PhD, is an internationally recognized consultant in the area of probiotic microbiology.
• She was the founding president and is currently the executive science officer of the scientific society, ISAPP. Dr. Sanders has authored over 120 peer-reviewed, scientific publications on efficacy substantiation, microbiology and regulatory issues pertaining to probiotics. Since 2017, She is Chair of the United States Pharmacopeia’s Probiotics Expert Panel and o-Chair of World Gastroenterology Organisation Committee preparing practice guidelines for the use of probiotics and prebiotics for GI indications.
• Conflicts of Interest Statement: The author declares receiving consulting fees by California Dairy Research Foundation, Church & Dwight, Mead Johnson, and PepsiCo; giving presentations in conferences sponsored by Kerry, Associated British Foods, Mead Johnson, Fairlife, GlaxoSmithKline, Trouw Nutrition, and serving on advisory boards for Cargill, Sanofi, Danone North America, Danone Research, Winclove Probiotics, and Yakult.

What is Xpeer?

Xpeer Medical Education is the first accredited medical education app in the market, with video microlearning engaging videos of just 5 minutes.

With a powerful algorithm to personalize the user experience and the contents as the most popular entertaining streaming platforms, it offers a brand new experience for the continuing education and professional development of the healthcare professionals.

Accredited by the European Union of Medical Specialists, it delivers high quality scientific medical education pieces. On Xpeer, you will find this curriculum on Microbiota and 500 hours of medical education in 2023 in your specialty, technologies and professional and personal skills.

Information on accreditation

The app Xpeer is accredited by the European Accreditation Council for Continuing Medical Education (EACCME) to provide official ECMEC credits recognized officially in 26 countries.

The credits for the users of the module will be 1 European CME credit (ECMEC®) for every hour (60 minutes of actual e-learning excluding introductions etc.) of use, provided that the users have completed a module and have passed the relevant assessment.

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There is no doubt, diet is the most effective means of modulating the composition of our gut microbiota. But studies are often limited to one nutrient (the effect of a protein, fiber, etc.) without evaluating the effect of the whole foodstuff. Well, all nutrients in a foodstuff interact, with antagonistic and synergistic effects, so much so that in real life, the overall effect of a foodstuff is rarely the sum of the individual effects of each of its components. Thus, almonds, as all seeds, are rich in lipids and therefore in calories (incidentally oil is extracted from them!) but also in fibers which act on intestinal transit, in polyphenols with anti-aging properties, etc.

To evaluate the effects of almonds on the gut microbiota, American almond producers have just funded a study which represents, in terms of quality, the Holy Grail in nutrition: a randomized (sidenote: Randomized trial Study in which the products tested are distributed randomly, between the participants. ) controlled trial (sidenote: Controlled trial a study in which participants are given either a test product (capsule containing the active compound) or a placebo (control capsule not containing the active compound), thus allowing for comparison. ) . Thus, 87 young volunteers little inclined to eat fruit and vegetables were distributed randomly between 3 comparable groups. Their mission: to consume, every day for 4 weeks, two snacks in place of their usual snacks, comprising either 2 handfuls of whole almonds, or the equivalent in ground almonds, or 2 muffins with the same calorie content (controls).

Disappointing results, limited health benefits

The least that can be said, is that the results observed will not have matched the level of investment. The authors hoped to observe that the almonds had a boosting effect on the intestinal bifidobacteria (sidenote: Bifidobacterium A genus of Y-shaped bacteria, most species of which are beneficial to humans. They are found in the gut of humans, and in some yogurts.

They:
- Protect the gut barrier 
- Participate in the development of the immune system and help fight inflammation 
- Promote digestion and improve symptoms of gastrointestinal disorders Sung V, D'Amico F, Cabana MD, et al. Lactobacillus reuteri to Treat Infant Colic: A Meta-analysis. Pediatrics. 2018 Jan;141(1):e20171811.  O'Callaghan A, van Sinderen D. Bifidobacteria and Their Role as Members of the Human Gut Microbiota. Front Microbiol. 2016 Jun 15;7:925. Ruiz L, Delgado S, Ruas-Madiedo P, et al. Bifidobacteria and Their Molecular Communication with the Immune System. Front Microbiol. 2017 Dec 4;8:2345. ) . Well, rather the opposite happened... They wagered on an accelerated intestinal transit due to the fibers present in the almonds: but no, the oily nuts changed nothing. The study even called into question a principle accepted up until then by nutritionists, namely that, unlike finely ground almonds, whole almonds would continue, even after mastication, to retain the lipid droplets in their structure. Well, the results show that the commercial grinding of almonds produces practically no differences in terms of lipid accessibility. In other words, your body will be able to assimilate the fats and calories of whole almonds, practically as well as those of ground almonds.

The exception: a short-chain fatty acid

Only one positive note was observed: the consumption of almonds (whole and ground) led to a significant increase in the production, by the gut bacteria, of a short-chain fatty acid (sidenote: Short chain fatty acids (SGFA) Short chain fatty acids are a source of energy (fuel) for an individual’s cells. They interact with the immune system and are implicated in communication between the gut and the brain.   Silva YP, Bernardi A, Frozza RL. The Role of Short-Chain Fatty Acids From Gut Microbiota in Gut-Brain Communication. Front Endocrinol (Lausanne). 2020;11:25. ) beneficial to our health, butyrate.

The almond producers of California have once again treated themselves to the Holy Grail of studies: a randomized controlled trial (RCT). Aim: to evaluate the impact of almonds and of their transformation (ground or not) on intestinal bifidobacteria and, secondarily, on the overall composition of the gut microbiota and intestinal transit time. To do this, 87 adults in good health, avid snackers (crisps, chocolate, etc.) and little inclined to consume fiber (fruit, vegetables, etc.), took part in this 3-arm trial: over 4 weeks, they replaced their 2 usual snacks either by whole almonds (2*23 g/d), or by ground almonds (2+23 g/d) or by 2 muffins with the same calorie content (control).

Almonds: the end of a nutritional myth?

Outcome? Contrary to the main hypothesis, bifidobacteria were not more abundant in the stools of the whole almond (8.7%) or ground almond (7.8 %) groups compared with the control (13.0 %), the opposite was the case. Nevertheless, the slight difference does not withstand an adjustment to the test. Almonds also have no effect on the gut microbiota, intestinal transit time (which the researchers thought was accelerated), stool consistency or intestinal symptoms. The particle size of ground almonds was finer than that of almonds after mastication: for all that, the effect of grinding on the release of lipids and therefore their accessibility by the organism proved smaller than anticipated, to the point that the researchers concluded that the commercial grinding of almonds does not lead to clinically significant differences in terms of nutrient bioaccessibility.
The only significant difference observed: the consumption of almonds (whole and ground) led to an increase in the production of butyrate by the gut bacteria (24.1 μmol/g vs 18.2 μmol/g for the control), a short-chain fatty acid with recognized health benefits, which, according to the authors would suggest a modification of the functions of the gut microbiota. 

No prebiotic effect 

It is without doubt a disappointment for the American producers but, according to this RCT, the consumption of almonds does not exert a prebiotic effect on the fecal bifidobacteria, produce major changes in the microbiota, or affect transit. Could the predominance of women (86.2%) and young people (27.5 ± 6.2 years) in the volunteers have biased the results? Perhaps. In the meantime, other studies are expected targeting a more uniform population to confirm these results. 

It’s all common sense. Often too rich in fat and sugar, the “Western (sidenote: Western diet Diet rich in processed foods, refined sugar, salt, saturated fats (red meats) and trans fats (pastries) Zinöcker MK, Lindseth IA. The Western Diet-Microbiome-Host Interaction and Its Role in Metabolic Disease. Nutrients. 2018 Mar 17;10(3):365.  ) ” diet has an impact on our health. It tends to increase inflammation in the body and to disrupt the metabolism. It can thus lead to obesity, type 2 diabetes, and metabolic syndrome. Numerous studies have shown that the gut microbiota and its immune system play a major role in metabolic balance, with disturbances in the gut converting excess food into extra pounds and serious illnesses.

More fat and sugar means less gut immune cells to balance the metabolism 

To better understand these disturbances, researchers fed mice a diet rich in fat and sugar for four weeks. As expected, in addition to gaining more weight than mice fed normally, these overfed mice also developed a metabolic syndrome (sidenote: Metabolic syndrome Combination of several metabolic anomalies: high blood pressure, large waist circumference, increased blood triglyceride and glucose levels associated to a low blood level of “good” cholesterol. Alberti KG, Zimmet P, Shaw J. The metabolic syndrome--a new worldwide definition. Lancet. 2005 ; 366 (9491) : 1059-62. ) . An analysis of the mice’s gut flora via their droppings showed that this diet caused a rapid loss of segmented filamentous bacteria (sidenote: Segmented filamentous bacteria Segmented filamentous bacteria (SFB) are bacteria of the Clostridiaceae family that colonize the gut of many vertebrate and invertebrate animals without causing an inflammatory response. On the contrary, their presence is thought to stimulate the immune response. They help in the differentiation and maturation of certain defense cells and promote the elimination of pathogenic microbes.  Hedblom GA, Reiland HA, Sylte MJ, et al. Segmented filamentous bacteria–metabolism meets immunity. Frontiers in microbiology. 2018 Aug 24;9:1991.  https://www.frontiersin.org/articles/10.3389/fmicb.2018.01991/full   ) . This in turn reduced the production of T helper 17 (Th17) immune cells (sidenote: T helper 17 (Th17) cells Th17 cells are immune system cells that play a role in host defense against pathogens, particularly at epithelial barriers, such as the gut barrier. Awasthi A, Kuchroo VK (2009) Th17 cells: From precursors to players in inflammation and infection. Int Immunol 21:489–498. ) , subsequent to which the metabolic syndrome appeared. 

The researchers found that Th17 cells regulate the absorption of lipids in the gut and are necessary for protection against metabolic syndrome. The loss of Th17 cells is thus to blame for the adverse health effects of a diet high in fat and sugar. By administering segmented filamentous bacteria to the overfed mice, Th17 production was restored. As a result, the mice lost weight and their metabolism improved.

Sugar, the metabolism’s worst enemy 

But which is most to blame, too much fat or too much sugar? The effects of a diet rich in fat and sugar (including sucrose and maltodextrin, common in candy and soda) were compared with those of a diet rich in fat but low in sugar. The researchers found that sugar on its own modifies the composition of the gut microbiota to the detriment of the segmented filamentous bacteria that stimulate Th17 cells. So would it be enough to eliminate sugar from the diet to ensure protection against metabolic disease? Not entirely, according to the researchers, since protection also requires the presence of the Th17 cells produced by the gut microbiota.

In short, metabolic syndrome, obesity, and type 2 diabetes are the result of complex interactions between diet, the gut microbiota, and immunity. According to the researchers, there is no “universal” diet that would produce the desired effect in everyone. Instead, a personalized approach to metabolic disorders is required. In the future, such approaches could take into account inter-individual differences in the gut microbiota’s immune system.

Vaccines are one of the greatest successes of public health, saving millions of lives worldwide, especially among young children (0-5 years), who are more vulnerable to infectious diseases. However, their efficacy varies from one population to another, with higher rates of protective immunity in European countries than in low- and middle-income countries (LMIC). Since the development of the gut microbiota in early life is intimately linked to the maturation of the immune system, and the microbiota of children in LMIC differ significantly from those of European children, researchers reviewed the evidence pointing to the gut microbiota’s role in disparities in vaccine response.

Immunomodulatory properties

A study on vaccines against tuberculosis, tetanus, hepatitis B, and poliomyelitis in Bangladeshi infants found that the presence of certain taxa is correlated with the rate of vaccine response, positively in the case of Actinobacteria, but negatively for Enterobacteriaceae. In addition, interventions to modify the microbiota (prebiotics, probiotics, antibiotics) provide further evidence of its involvement in vaccine response. A 2018 systematic review summarized the results of 26 studies in humans that used probiotics to enhance the efficacy of various vaccines. The review found positive outcomes in half the studies. Conversely, studies investigating the effects of antibiotics found either no improvement or a reduced immune response, which was attributed to disruption of the microbiota.

Two bacterial genera especially involved 

Two bacterial genera seem particularly capable of modulating responses to vaccines. Bifidobacterium and Bacteroides are essential for the development of a healthy microbiota in young children. However, young children can face significant microbiota disruptions (cesarean section, etc.). The effects of the microbiota on vaccine responses appear to be mediated by certain metabolites and/or cellular components, such as short-chain fatty acids, exopolysaccharides, or extracellular vesicles.

Towards a new generation of vaccine strategies

Although the relevant strains and products need to be better characterized, the intricate relationship between the microbiota and vaccine efficacy opens up rich clinical perspectives. This includes new vaccine stimulation therapies able to improve protection for children from LMIC without the use of adjuvants, which are often thought to have adverse side effects.