We are often told not to abuse antibiotics, but the use of antibiotics to treat conditions other than bacterial infections is still too common, with consequences for our health. Indeed, exposure to antibiotics during the first months of life may be associated with the subsequent development of asthma, an inflammatory disease of the respiratory system (sidenote: https://www.who.int/news-room/q-a-detail/asthma ) . Alterations in the intestinal and nasal microbiota are recognized as a risk factor for the development of the disease and an indicator of its severity. Knowing that antibiotics alter bacterial communities, a team of researchers considered whether alterations of the nasal microbiota can explain the development of childhood asthma.

Link between antibiotics and asthma established

A team studied a group of around 700 children to search for a link between antibiotic exposure before the age of one and the development of asthma at the age of seven. In total, half of the children had received antibiotics in their first eleven months and almost 8% of them subsequently developed asthma. This proportion rose to over 11% among those treated with two or more antibiotics before eleven months, an increase of 4% compared to the children not exposed to antibiotics.

Moraxella, the main absentee from the nose

The researchers observed that the nasal microbiota changes during the first two years of life and that antibiotic therapy before the age of one impacts babies’ nasal flora, with this impact growing as the number of treatments increases. In particular, the absence from the nose of Moraxella–a bacterium often associated with respiratory diseases–seemed to signal an early and significant exposure to antibiotics. Their use before the age of one may therefore have long-term harmful effects on the nasal microbiota, facilitating the cascade of events that lead to the development of asthma. Even if other factors, such as the intestinal microbiota or the immune system, are also involved, these results still support current recommendations for the prudent use of antibiotics, especially among infants.

Global prevalence of obesity almost tripled between 1975 and 2016 and now represents a major public health issue. Bariatric surgery is currently the best strategy for achieving lasting weight loss in patients suffering from morbid obesity1, with a five-year success rate of over 66%. It mainly consists of two techniques of comparable effectiveness: gastric bypass (or more precisely, laparoscopic Roux-en-Y gastric bypass) and sleeve gastrectomy, which involves removing two-thirds of the stomach. How do these interventions affect the bacterial ecosystem? Do the two approaches have the same impact?

Enriched and diversified intestinal microbiota

To find out, researchers compared two groups of around 100 patients, one subjected to gastric bypass and the other to sleeve gastrectomy. Six months later they observed a significant increase in bacterial abundance and diversity in the gut microbiota of all participants. 40% of bacteria were common to both approaches, including Akkermansia muciniphila–known to be negatively correlated with obesity–, as well as certain proteobacteria such as Escherichia coli, suspected of influencing both appetite and metabolism after surgery. However, only the gastric bypass caused a depletion of Faecalibacterium prausnitzii, a species associated with certain metabolic disorders and inflammatory bowel diseases.

Gastric bypass has a greatest impact

Both approaches also resulted in increased transport systems for vitamins B₁₂ and B₁, manganese, iron, and zinc, suggesting increased use of these nutrients by bacteria. According to the authors, the impact of gastric bypass was greater than that of sleeve gastrectomy in all aspects. However, they consider that a further three to five years will be required to establish whether these discoveries have the clinical ability to preferentially direct patients towards one treatment or the other.

^{1. Morbid obesity is defined by a body mass index (BMI) of over 40}

IBDs, Crohn’s disease and ulcerative colitis (UC), are characterized by inflammation in the wall of part of the digestive tract, which is related to hyperactivity of the digestive immune system. During IBD flares, the most common symptoms are abdominal pain and diarrhea, which can sometimes be hemorrhagic. These diseases can also present signs in systems outside the digestive tract, including joints and the ophthalmic, cutaneous, and hepatic systems.

IBDs affect 1 person in every 1000 in Western Europe and most often appear between 20 and 40 years of age. These illnesses follow intermittent courses, with alternating periods of flares and remission. In Crohn’s disease, this inflammation can be localized at all stages of the digestive system, from the mouth to the anus, although it is most often found in the intestine. Ulcerative colitis is localized in the rectum and colon.

Multifactorial disorders

The causes of IBDs include genetic predisposition, environmental factors like pollution and diet, the immune system, and intestinal microbiota. IBDs may also be caused by a lack of exposure to microorganisms during childhood due to an excessive hygiene, for example.

Modified intestinal content

Intestinal microbiota seems to play an important yet still poorly understood role in the characteristic inflammation of IBDs. Numerous studies have observed dysbiosis in these patients, i.e. a change in the microbiota equilibrium, linked to genetic and environmental factors. Anti-inflammatory bacteria in particular are weakened. This imbalance changes the content of the intestine and can lead to chronic inflammation.

Hope for treatment

There is no curative therapy, but anti-inflammatories can limit painful flares. Treatment currently includes corticosteroid therapy, treatments called “immunomodulators” that can reduce the immune system’s reactions, like anti-TNFα, and surgery in 80% of Crohn’s cases and 20% of UC. It rarely provides a definitive cure. Researchers are currently trying to target the role of microbiota in IBDs, trying to reduce the presence of pathogens and boost the growth of good microorganisms.

Three times more common than 30 years ago, today, eczema affects up to 20% of children. It has become the most common childhood cutaneous condition in industrialized countries. However, in the majority of cases, eczema disappears in adolescence, and only 10 to 15% of patients remain affected throughout their lives.

An excessive immune response

Eczema is related to a genetic predisposition that alters the skin barrier. This alteration paves the way for allergens to penetrate into the skin, which causes an excessive immune reaction. Changes in the composition and diversity of the intestinal and cutaneous microbiotas observed in these patients may also be involved.

Eczema manifests very early in infancy (between 1 and 3 months) by rough, dry skin, and the appearance of very itchy red patches during inflammatory flares.

Limit skin irritation

Treatment for eczema primarily tries to limit skin irritation (wearing cotton clothes, using gels without soap, being gentle when washing your skin, etc.) and to reduce cutaneous lesions with hydrating creams and topical steroids. In the most severe cases, the doctor may prescribe short-term antihistamines.

Probiotics improve symptoms

Another approach: correct the dysbiosis (imbalance in bacterial flora) by modifying the intestinal and cutaneous microbiotas. Several studies have shown that probiotics improve eczema symptoms (particularly certain lactobacilli) and reduce intestinal inflammation in affected babies. Given as a preventative treatment to pregnant women, they could reduce the frequency of symptoms in their baby.

What is asthma?

Asthma is a chronic disease of the respiratory system that manifests itself as coughing, wheezing, shortness of breath, tightness in the chest, or a combination of these symptoms.¹ Symptoms are caused by a narrowing of the airways in the lungs due to inflammation of the bronchi.¹ Asthma attacks occur more frequently at night or during physical activity and the severity and frequency of attacks vary from patient to patient.¹ 

Predispositions and triggers for asthma

Asthma is a complex multifactorial disease. It can develop due to a genetic predisposition (allergic background) and/or exposure to environmental factors such as allergens (pollens, mites), tobacco smoke or air pollution. Strong emotions, cold air or physical exercise can also trigger attacks. Lastly, individual-specific factors, such as an infection, or even obesity, can also come into play.²

Link with the microbiota?

Numerous studies note the role played by the various microbiota in the disease:

Living with asthma: treatments and solutions?

Although asthma cannot be cured, there are treatments that allow asthma patients to lead normal and active lives. Symptomatic treatments mainly limit the intensity of acute attacks by opening the bronchi, while disease-modifying treatments reduce inflammation of the airways, thus improving respiratory function and reducing attack severity.¹

Studies on the relationship between the microbiota and asthma suggest that modifying the microbiota could help prevent the disease, leading researchers to focus their efforts on the use of probiotics and prebiotics.^16,17 Their use as a treatment for the disease is also being studied.¹⁸

Are there any protective factors?

Exposure to microorganisms (sidenote: Microorganisms Living organisms that are too small to be seen with the naked eye. They include bacteria, viruses, fungi, archaea and protozoa, and are commonly referred to as “microbes”. What is microbiology? Microbiology Society. ) during early childhood seems to help prevent asthma. Contrary to popular belief, living in a sanitized environment does not necessarily protect against respiratory diseases. Some studies show that house dust is not necessarily a risk factor for the development of the disease,¹⁹ while others have shown a decreased risk of asthma in children born and raised in the countryside²⁰ or with pets.²¹

BMI-21.27

400 million sufferers 

Tickling sensations, sneezing fits, watery eyes, itching, a blocked or runny nose... Although very common, allergic rhinitis has a real impact on sufferers’ quality of life.  Approximately 400 million people suffer with this respiratory allergy1. 
Allergic rhinitis is described as seasonal (known as “hay fever”) when it is linked to tree, grass, or herbaceous pollens. It is described as perennial when it is due to allergens that are present all year round, such as dust mites, molds, or animal hair (cats and dogs) ². 

The symptoms of allergic rhinitis 

Allergic rhinitis has very characteristic symptoms, usually a combination of ³: 

• Pruritus (itching, irritation) 
• Anosmia (loss of smell) 
• Rhinorrhea (runny nose) 
• Repeated sneezing 
• Nasal obstruction (blocked nose) 

In seasonal allergic rhinitis and perennial allergic rhinitis, these symptoms are exacerbated. 

Modified microbiota 

Imbalances in the gut microbiota and in the ENT microbiota (ear-nose-throat microbiota), also known as “dysbiosis”, have been demonstrated in cases of allergic rhinitis. This dysbiosis is characterized by a low diversity of the gut microbiota ^4,5, and a composition of the ENT microbiota (ear-nose-throat microbiota) that differs from that of healthy individuals ^6-8. Finally, all the factors that can impact the gut microbiota (antibiotics, diet, etc.) during the perinatal period may have long-term effects on allergy susceptibility ⁹. 

Treatments for allergic rhinitis 

The treatment of allergic rhinitis is based on 3 approaches: avoidance of allergens, medication and desensitization. There are also symptomatic treatments to improve comfort ¹⁰. Finally, the approach of correcting 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.   ) and rebalancing the microbiota with probiotics is being studied, with promising results. These probiotics seem to be effective in improving the symptoms of allergic rhinitis and enhancing patients’ quality of life ¹¹. 

BMI-23.17

Food allergies are a dysfunction in the immune system, which reacts abnormally immediately after ingestion of a specific food. The food, normally harmless to the body, is then called an “allergen.” These allergies affect 3% of the general population and 5% of children.

Many foods to blame

Products likely to trigger a food allergy are numerous and vary according to age and the person’s food habits. Governmental sites regularly update the list of identified allergens. Children are more sensitive to eggs, peanuts, and cow’s milk, whereas adults are more sensitive to crustaceans and mollusks, certain fruits, and soy.
In contrast with food intolerances, food allergy symptoms appear violently: they can be digestive, respiratory, or cutaneous. Angioedema, asthma attacks, and anaphylactic shock are life-threatening emergencies.

Imbalance in the microbiota

It has not yet been explained why certain foods cause an inappropriate immune reaction. Studies very quickly established a connection between these allergic phenomena and an alteration in the microbiota: allergic patients all have a different microbiota compared to healthy individuals. Observations of dysbiosis in affected people have shown that certain bacteria are responsible for the appearance of hypersensitivity to dietary proteins.

Probiotics as prevention?

Although the primary treatment for food allergies is removing the offending food, numerous studies have suggested that modulating the microbiota with probiotics and prebiotics may prevent the development of allergies.

Alcohol and obesity, causes of liver disease

Liver diseases (hepatopathies) present varying degrees of severity, ranging at one extreme from steatosis, which is benign and reversible, to hepatic inflammation (NASH), hepatitis, fibrosis, cirrhosis and, at the other extreme, to hepatocellular carcinoma (liver cancer). Asymptomatic in their less serious forms, liver diseases can present with jaundice, nausea, and fever in their advanced forms.

Alcohol abuse is a known cause of diet-based liver disease (alcoholic liver diseases or ALD), however excess weight and obesity are less well-known. The metabolic steatosis (or NAFLD) that they cause represents the primary cause of chronic liver diseases in industrialized countries.

Intestinal dysbiosis, cofactor in liver disease

It seems that these risk factors are not enough to induce hepatopathy on their own. The existence of an imbalance in the intestinal microbiota is also involved. The evidence for this is that all patients with liver disease, regardless of the cause, present with dysbiosis and a change in the intestinal barrier. The more serious the liver damage, the more significant the dysbiosis.

Probiotics, prebiotics, and fecal transplant, three promising avenues for research

Current treatment for liver disease includes lifestyle and diet changes (weight loss and physical activity), with or without associated medical treatments, which can range in complexity (medication, liver transplant).

The role of the microbiota is now clear, so modifying it with prebiotics, probiotics, and fecal transplant constitutes a promising avenue for preventative and therapeutic research.

Recommended by our community

Metabolic syndrome is not, strictly speaking, a disease; its definition is the existence, in a single person, of abdominal obesity (waist measurement > 94 cm for men, 80 cm for women), associated with at least two of the following problems: abnormally elevated insulin level, hypertriglyceridemia, high blood pressure, hyperglycemia, or low HDL cholesterol (“good cholesterol”).

France spared

With 14 to 21% of people affected, compared with a quarter of Americans and almost 46% of Greeks, France has been somewhat spared the “epidemic” of metabolic syndrome. But this situation cannot last.

Unhealthy lifestyle, the primary risk factor

Other than likely genetic predispositions, it’s an unhealthy lifestyle that leads to metabolic syndrome. Junk food, paired with insufficient physical activity, causes metabolic dysfunction that leads to chronic inflammation, which itself causes metabolic disorders. It starts a vicious cycle, in which one contributor is imbalance in the microbiota or dysbiosis.

No visible signs

Other than obesity, metabolic syndrome has no visible signs since, once symptoms appear, it means that the syndrome has changed into a disease: type 2 diabetes, atherosclerosis, cardiovascular disease, etc.

Eat better, move more

For the time being, there is no treatment for metabolic syndrome. The only medical advice that works equally well as a prevention and a cure is a balanced diet with an emphasis on low glycemic index foods and regular and sustained physical activity. If the idea that probiotics and prebiotics as regulators of diet and weight is confirmed, it could also be factored into treatment for metabolic syndrome.

Microbiota: At the heart of our health

The MICROREVEAL series aims to raise awareness about the importance of microbiota in our daily lives. After a 1st episode focusing on imbalances in vaginal microbiota, journalist Louise Ekland is moving on to intestinal microbiota. Better known as “intestinal flora”, this microbiota is made up of more than 100 trillion microorganisms (bacteria, yeasts, viruses, and so on) and is one of the richest microbiota in our bodies.

Its role in diarrhea, among other things...

In this new episode, Julie suffers from diarrhea. To help shed light on this issue, Louise interviewed Dr. Alexis Mosca. Our intestinal microbiota is a genuine ecosystem that evolves over the course of our lives and varies according to several external factors – such as our diets or use of antibiotics – and internal factors – including our geographic origins. Its composition is thought to be associated with numerous illnesses (antibiotic-associated diarrhea, allergies and so on.)