Protecting Intestinal Microbiota From Antibiotic-Induced Disruption

What is the human Intestinal microbiota?

The human intestinal tract is naturally colonized by a huge bacterial population. The gut contains 10 times more bacteria than there are cells in the human body, i.e. 100 trillion bacteria! This microbial population, called intestinal flora, communal bacteria or gut microbiota, contains thousands of different bacterial strains. The microbiome (the aggregate of all the genes coming from the bacterial population) of the gut microbiota is considered by some scientists as a "second" genome. It indeed contains more than 3.3 million genes: 150 times more than the number of genes in the human genome!

Understanding the relationship between intestinal microbiota and human health is of utmost importance: recent findings suggest that human health is highly dependent upon the balance of gut microbiota. It indeed contributes to the digestion of certain foods, acts on the immune system and is a barrier against many harmful bacteria.

Intestinal microbiota is severely damaged during the course of an antibiotic treatment

The vast majority of orally administered antibiotics are only partially absorbed into the bloodstream via the intestinal tract, and for some of them, a significant part of the administered drug remains intact before crossing the ileo-caecal and reaching the colon. A similar phenomenon occurs for parenterally administered antibiotics that are recycled, via the hepatobiliary route, from the blood into the small intestine.

Thus, for both oral and parenteral antibiotics, active residues reach the colon at doses that are lethal for most commensal bacteria. The residues thereby provoke serious collateral damage amongst the intestinal microbiota of patients: several bacterial populations are erased whereas other (sometimes dangerous) strains proliferate. Their gut microbiota balance is hence durably disturbed; antibiotic treated patient will need several months for his/her gut microbiota to recover (i.e. to get back to the anterior equilibrium).

Antibiotic-induced microbiota disruption can lead to Clostridium difficile infection, a severe form of bacterial infection of the intestinal tract

Clostridium difficile counts among the bacterial strain most likely to proliferate after gut microbiota balance disruption. Clostridium difficile bacteria are indeed frequently resistant to antibiotics and can therefore take advantage of the liberation of previously taken ecological niches in the gut to rapidly outnumber harmless commensal bacteria. Their proliferation causes Clostridium difficile infections (CDI).

According to the Center for Disease Control and Prevention (CDC), CDI were estimated to afflict a half a million people in the United States in 2011, and 29,000 of them died within 30 days of the initial diagnosis. Those most at risk are people, especially older adults, who take antibiotics and are hospitalized.

You will find an illustration of the Clostridium difficile infection in the first part of the DAV132 video.

Several scientists have begun to acknowledge the essential role played by intestinal microbiota in health and general wellness

In Missing Microbes, Prof. Martin Blaser, the director of the Human Microbiome Program at New York University, reaches back to the discovery of antibiotics and traces how our subsequent overuse of these seeming wonder drugs has contributed to the rise of what Prof. Blaser calls our modern plagues: obesity, asthma, allergies, diabetes, and certain forms of cancer. Prof. Blaser’s studies suggest antibiotic use during early childhood poses the greatest risk to long-term health. Alarmingly, American children receive on average seventeen courses of antibiotics before they are twenty years old. See video of Martin Blazer introducing Missing Microbes.

Moreover, the results of a recent study suggest that antibiotic use may influence weight gain throughout childhood and not just during the earliest years1.

Additionally, in her book Gut, Giulia Enders raises awareness among the public about the key role played by intestinal bacteria in health by participating to metabolic reactions and acting as protective agents against pathogens.

Intestinal Bacteria are also a Reservoir for Antibiotic Resistance

When antibiotic residues reach the colon, they kill a high number of beneficial bacteria, and therefore exert a selective pressure which participates to the selection of resistant strains. This selection is particularly strong in the caecum, a region populated by a particularly prolific bacterial population due to a high concentration of nutrients. When resistant bacteria thrive in the gut, they exchange antibiotic resistance genes with other, potentially pathogenic, bacteria and contribute to the rise of antibiotic resistance which threatens current medical practice.

Learn more about Antibiotic Resistance.

Protecting intestinal microbiota during antibiotic treatment is therefore essential to preserve short-term and long-term health

Antibiotic-induced microbiota disruption is associated with Clostridium difficile infections, the emergence of resistant bacteria and chronic diseases such as obesity and asthma. Preventing the impact of antibiotics on the gut would thus participate to the prevention of these conditions.

Discover how DAV132 protects intestinal microbiota from antibiotic-induced disruption.


(1) B. S. Schwartz and others, ‘Antibiotic Use and Childhood Body Mass Index Trajectory’, International Journal of Obesity, 2015