They fight bacterial infections and save lives, but antibiotics, if used improperly, can also alter the functions of the intestinal immune system, promoting inflammation and the risk of cancer. Not only that: they can even decrease the effectiveness of cancer therapies. This is demonstrated by a study by researchers from the Department of Experimental Oncology of the European Institute of Oncology (IEO) in Milan who, coordinated by Federica Facciotti and Francesco Strati, studied the effect that some broad-spectrum antibiotic therapies can have on experimental models, such as vancomycin and streptomycin. The research results are published in the journal Microbiome.
Antibiotics have revolutionized the treatment of bacterial infections and still save millions of lives, the problem is that they do not limit themselves to acting on the pathogenic germs for which they are prescribed and administered, but can modify the composition and biodiversity of the intestinal microbiota. ie the community of all microorganisms? billions of bacteria, fungi, archaea, protozoa and viruses – which inhabit our digestive system. And do it without distinction, hitting enemy or friendly species. But by damaging the biodiversity of the microbiota, antibiotics compromise the balance, i.e. homeostasis, between the microbiota and the immune system, decreasing the colon’s ability to control inflammation or resist attack by new pathogenic bacteria. The alteration of the microbiota, or dysbiosis, caused by antibiotics compromises the normal function of the T lymphocytes of the intestinal wall and of the immune cells called iNKT (Invariant Natural Killer T).
The clinical value of the research
“Our discovery has great clinical value for the prevention and treatment of important diseases such as inflammatory bowel diseases, for example Crohn’s disease and ulcerative colitis, which, in addition to having a negative impact on quality of life of those affected, are linked to an increased individual risk of developing colon cancer “, explains Facciotti:” Epidemiological data have already highlighted the link between the use of broad spectrum antibiotics and increased risk of developing functions aberrants of the immune system. We have investigated why and demonstrated it in experimental models of the disease. In summary, antibiotic therapy breaks the compensation mechanisms between the microbiota and the immune system, depriving the body of the most effective natural barriers against various diseases of the digestive system, including colon cancer “.
Pro-inflammatory antibiotics
However, we must not make a bundle of the whole herb: “Antibiotics have different mechanisms of action and for this they can alter the microbiota differently following their use”, continues Strati: “We have discovered that the use of vancomycin and streptomycin modifies the microbiota to the point of favoring the increase of microorganisms with pro-inflammatory characteristics, compromising the correct functionality of the immune system. The use of metronidazole, on the other hand, has maintained the immune system’s ability to control intestinal inflammation by promoting the expansion of microbial species with anti-inflammatory properties, despite its use having in any case altered the composition of the intestinal microbiota “.
Cancer therapies work less
“In recent years it has been understood that the alteration of the intestinal microbiota due to the use of antibiotics makes anticancer therapies less effective precisely because it weakens the functions of the immune system, which are fundamental in the success of oncological therapies”, Facciotti goes on. : “At this moment in the laboratory we are studying how the alterations of the microbiota in colon cancer patients contribute to weaken the immune system and therefore to decrease the ability of patients to effectively fight colorectal cancers”.
Proper nutrition and friendly bacteria
Next step? “Finding ways to restore the altered microbiota to a state of normality”, concludes the researcher: “For example through the diet or with the administration of good bacteria, in order to support the anticancer functions of the immune system”.
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