You may have heard that triclosan has been banned from hand soaps. NewScientist (17 December 2016, paywall) now has some details on a potentially worse situation because of how triclosan functions in relation to bacteria – which is, by stopping them, rather than destroying them.
Now there’s reason to worry over even more serious effects. To see whether antibacterials can affect the performance of antibiotics, Petra Levin and Corey Westfall, at Washington University in St Louis, Missouri, exposed Escherichia coli to common antibiotics and triclosan, and measured their survival over 20 hours.
When the bacteria were exposed to the antibiotics streptomycin or ciprofloxacin, plus triclosan, they were 10,000 times more likely to survive than those that weren’t also given triclosan. Further tests found that triclosan protects the MRSA superbug against vancomycin, a crucial antibiotic often used as a last resort in MRSA infections (bioRxiv, DOI: 10.1101/090829).
We don’t know why triclosan has these effects, but one explanation might lie in the different ways that antibiotics and antibacterials work. Most antibiotics kill bacteria by interfering with essential steps in their life cycle, such as making cell walls. Since triclosan prevents bacteria from growing, they may not go through as many life cycle stages, becoming impervious to antibiotics as a result. “A dormant cell has not a lot of active targets, so there’s not much to corrupt,” says Kim Lewis at Northeastern University in Boston.
One of those results which reminds me that reality is far more bizarre than I can imagine sometimes.
