Year in review: Microbes exploit their killer

Triclosan promotes antibiotic resistance

ANTIBACTERIAL BACKFIRE Triclosan, an unregulated antimicrobial chemical found in consumer products such as soaps and toothpaste, may aid, rather than deter, microbes that invade people’s bodies.

By Beth Mole

December 15, 2014 at 7:00 am

Microbes have turned our pharmaceutical weapons into allies. This year, triclosan, an antimicrobial agent, topped the list of chemical traitors, aiding rather than deterring germs.

Leaked from products such as toothpaste and hand soap, low doses of triclosan promote drug resistance in germs that cause difficult-to-treat infections. In the environment, the chemical can disrupt hormone regulation in some animals, such as fish. (Data are lacking on health effects in humans.)

Despite the ongoing battle against antibiotic-resistant microbes (SN: 10/4/14, p. 22), triclosan remains omnipresent in household and personal care products. Humans take up the anti-microbial agent by ingesting it or absorbing it through skin. Washed down the drain, triclosan amasses in sewage and seeps into the environment.

graph of triclosan in nasal secretions — People with high concentrations of triclosan in their nostrils are more likely to harbor *Staphylococcus aureus* bacteria in their noses than are people with low levels of the antimicrobial chemical, a study in 2014 found. A.K. Syed *et al*/*MBio* 2014

In people, the chemical shows up in blood, urine, breast milk, umbilical cords and snot. The health risks of prenatal doses of triclosan are unknown. In the nose, however, researchers found that triclosan-laced snot helps Staphylococcus aureus

bacteria invade the body ( SN: 5/17/14, p. 12 ). Such invasions increased the risk of staph infections, which can cause pneumonia.

In wastewater treatment plants, triclosan can sabotage the microbial cleaners responsible for breaking down sewage, killing off some beneficial microbes and spurring drug resistance in others (SN: 7/26/14, p. 9).

Some of the 100 metric tons of triclosan that enters U.S. sewage plants each year lingers after treatment. Treated waste-water and sewage-based fertilizers can then spread the antimicrobial chemical. When such treated water is used on farmland, small amounts of triclosan accumulate in vegetables (SN Online: 9/19/14).

The U.S. Food and Drug Administration is reviewing the use of triclosan in personal care products. But some legislators and manufacturers aren’t waiting. In May, Minnesota banned triclosan from certain products, effective in 2017. And Johnson & Johnson and Procter & Gamble plan to remove the antimicrobial agent from their products.