A common household ingredient could sabotage your antibiotics


Photo of a 2009 toothbrush with Colgate Total toothpaste, a brand that once contained triclosan. The company has changed only this year.
Photo: Carolyn Kaster (AP)

Your new daily dose of toothpaste or body spray may be wasting your antibiotic treatment, suggests new research. It has been found that a common household antimicrobial ingredient – triclosan – appeared to reduce by a hundred times the potency of the antibiotics used to treat urinary tract infections, at least in mice.

Triclosan is a ubiquitous chemical found in everything from body cleansers to lip glosses to deodorants, household cleaners and mouthwashes. Traditionally, it has been reported that it was an easy way to kill bacteria and fungi, apparently without harming humans. In recent years, however, more and more evidence suggests the opposite.

In 2017, the Food and Drug Administration finalized its ban on using triclosan and similar chemicals in consumer soap products marketed as antimicrobials. The agency cited evidence that antimicrobial soaps containing these ingredients did not seem to prevent disease or even kill bacteria better than a bar of soap and hot water. What is even more disturbing is a growing body of evidence showing that triclosan can actually help create bacterial superbugs.

It is thought that the way in which triclosan stops bacteria is too similar to the number of antibiotics that do the work. Thus, bacteria that develop resistance to triclosan also learn to repel these drugs. This is definitely bad news because triclosan ends up everywhere in our environment, where it can promote broad resistance to antibiotics.

The new study, published in Antimicrobial Agents and Chemotherapy, did not innovate with respect to this relationship. But the results suggest that the effects of triclosan on antibiotics and bacteria occur long before the chemical escapes into the outside world – this can also happen inside our body.

The researchers first exposed petri dishes containing infection strains causing urinary tract infections. Escherichia coli and resistant to methicillin Staphylococcus aureus (the superbacterium also called MRSA) at doses of triclosan that you usually find in a consumer product. Then they tried to use common antibiotics, killing the bacteria. Compared with unexposed bacteria, triclosan-coated bacteria were able to tolerate antibiotics 1,000 times better. The team then did a similar experiment with live mice, discovering that the bacteria exposed to triclosan could survive in mice up to 100 times better than control germs.

"Normally, one in a million cells survive antibiotics and a functioning immune system can control them. But triclosan was changing the number of cells, "said a statement by Petra Levin, a professor of biology at the University of Washington. "Instead of just one out of a million surviving bacteria, one in ten survived after 20 hours. Now the immune system is outdated. "

Mice are not human beings. The study is therefore limited to what it can tell us about antibiotic resistance in humans. That said, there is something to be worried about. Urinary tract infections, especially in women, are one of the most common infections for which we rely on antibiotics. And even with the ban on antimicrobial soap, triclosan is still very prevalent. Other research has shown that nearly three quarters of Americans absorb enough triclosan for it to be present in the urine.

Perhaps Levin's work has also uncovered one of the reasons why triclosan can prevent certain antibiotics from working. His team found evidence that the chemical triggers the production of a molecule called ppGpp that slows bacterial growth. According to them, these slower bacteria can then better fight certain antibiotics. By mutant E. coli unable to make the team-created ppGpp, triclosan could not stop antibiotics from working, adding additional support to their theory. It is likely, however, that ppGpp is just one of many ways that triclosan can affect antibiotic resistance.

Whatever the case may be, at least some companies that incorporate triclosan into their products are starting to feel the heat. Earlier this year, Colgate-Palmolive launched a version of Colgate Total toothpaste without triclosan. While continuing to argue that the original version, the only American brand of toothpaste approved to carry triclosan, was perfectly safe and better for dental health than the competition, the company now claims that its new version, made of stannous fluoride, " offers even more benefits. "

If you do not know if you currently use products containing triclosan, the US Department of Health and Human Services has a handy list that you can consult.


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