Triclosan, a common antibacterial agent in household products, may actually promote the growth of Staph bacteria in people heavily exposed to it.
Trouble with triclosan. I'm Bob Hirshon and this is Science Update.
A anti-microbial agent used in household products may actually help Staph bacteria colonize people. This according to University of Michigan developmental biologist Blaise Boles. He explains that with enough exposure, triclosan works its way into people’s bodies.
And our results showed that if a person had triclosan in their nasal secretions, they were about twice as likely to have the bacterium Staphlococcus aureus in their nose.
What’s more, exposing lab rats to triclosan made them more vulnerable to Staph infections. Other evidence indicates that in low concentrations, triclosan can, in fact, help some bacteria rather than kill them. And while nasal Staph bacteria aren’t usually a big health risk, they can threaten patients weakened by other illnesses, and increase the chance of post-surgical infections. I’m Bob Hirshon for AAAS, the Science Society.
Making Sense of the Research
You see two kinds of soap on a drugstore shelf. One is labeled “antibacterial,” the other isn't. Which do you choose? Antibacterial is better, right?
Not so fast. So-called “antibacterial” products have certainly proven attractive to consumers. One of the most common antibacterial agents in these products, triclosan, may be found not only in soaps and body washes, but also in toothpaste, cosmetics, and even non-consumable products like clothing, furniture, and toys.
According to the Food and Drug Administration, triclosan isn't known to be directly hazardous to humans. And in a few cases, clinical studies have found benefits. For example, in 1997, FDA reviewed data on triclosan in a popular brand of toothpaste. The evidence showed that triclosan in this product was effective in preventing gingivitis.
However, in many other cases, the effectivness of triclosan is questionable at best. Although it's known to kill bacteria in sufficient concentrations given enough time, it's not at all clear that, for example, people generally spend enough time washing their hands to get any additional benefit from triclosan. Triclosan runoff does get into sewage systems, though, and has been found in the environment as well as the tissues of animals and people, raising concerns about long-term health consequences.
In this case, Boles and his team studied the relationship between having triclosan in one's body and Staphlococcus aureus bacteria in the nose. And they found that people with the antibiotic in their system were actually more likely to be colonized with Staph bacteria than those who didn't.
How can an antibiotic actually promote bacterial growth? Boles says there's lab evidence that when bacteria like Staph get exposed to less-than-lethal concentrations of triclosan, they get stressed, and as a defense, they boost the production of biofilms—sticky residues that keep bacteria attached to body tissues and other surfaces. It's sort of an example of the old saying, “What doesn't kill you makes you stronger.”
Many other studies also suggest that triclosan may promote the growth of antibiotic-resistant bacteria, by allowing the toughest strains to survive—although Boles doesn't think that's what's happening in this particular case. Still, triclosan has been used for over forty years, and as it becomes more and more prevalent in the environment and its living residents, it's feared that it may be doing more harm than good.
Now try and answer these questions:
- What is triclosan?
- What are some concerns about the effectiveness of triclosan?
- In this study, people with triclosan residue in their bodies were more likely to have Staph bacteria in their noses. Why do the researchers think this happens?
- Can you think of antibacterial products that you use in your everyday life? Does this change the way you feel about them? Why or why not?
You may want to check out these related Science Updates:
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- M.S. & Gut Bacteria
For another example of a common household chemical that may have a hidden cost, see the Science Update lesson Lawn Nitrates.