Using too many antimicrobial agents will increase the bacteria’s resistance to antibiotics. This is the conclusion of a study published in Journal of Antimicrobial Chemotherapy. However, more and more everyday products, in particular cosmetics, soaps, toothpastes or even hydroalcoholic gel contain it.
Researchers from the University of Birmingham and the Quadram Institute in the United Kingdom have specifically tested triclosan, an ingredient widely used in hygiene and cosmetics. This substance is already known to increase the risk of allergy, loss of muscle strength, damage to the immune system, and even liver cancer. Scientists have found that triclosan is often in too small an amount in consumer products to have any real antibacterial effect. On the other hand, the exposed bacteria come out stronger and more resistant to antibiotics.
Superbugs made even stronger
The study focused on the bacteria E. Coli and Salmonella and on strains carrying the gyrA mutation. In the presence of triclosan, these increase the activity of their stress response pathways and become even more resistant. It then takes four times more triclosan and eight times more quinolone (antibiotic used against these bacteria), to stop their proliferation. The bacteria of the E. Coli strain do not develop new mutations, but those which already have the gyrA mutation take precedence over the others. Triclosan therefore does not cause new resistance but strengthens existing ones. This study provides proof of concept that repeated low exposures to antimicrobial agents reinforce bacteria that already have mutations, thus participating in antibiotic resistance.
This worries experts in the field. Two hundred of them published a column on June 29 in the journal Environmental Health Perspective to warn about the dangers of triclosan and triclocarban. These two substances were found in almost all of the urine samples tested and can also be present in blood or breast milk. The authors of this column point out the dangers of these endocrine disruptors which promote resistance to bacteria, but also affect reproductive health and sensitivity to allergens. They remind that soap and water, or bleach do not cause such problems and should be preferred.
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