Bacteria developing resistance to hand sanitizers

Aggressive use of hand sanitizer to kill germs could backfire, according to a new study, which finds that when some hospitals upped their use of sanitizers, sanitizer-resistant bacteria emerged and proliferated throughout their wards.
By Rick Docksai | Jan 15, 2019
Bacteria can evolve to withstand the cleansing power of popular hand sanitizers, says a new study published in Science Translational Medicine. The study found that as hospitals increased their use of alcohol-based hand sanitizers, bacterial strains with higher "alcohol tolerance" emerged and grew more numerous throughout the wards.

The researchers, led by infectious disease expert Paul Johnson and microbiologist Timothy Stinear of the University of Melbourne, gathered bacterial samples from both hospitals over the years from 1997 to 2015. They analyzed the samples, looking for changes in the strains over time.

They especially focused on looking for E. faecium, a bacterium that's become a leading cause of infections in hospitals and often proves to be resistant to the existing antibiotics. This bacterium is growing more common even while other dangerous bacteria such as MRSA and staph have gone into decline, according to Johnson and Linear. They added that another trend coincides with these two: Hospitals everywhere have been increasing their use of sanitizers.

The researchers suspected a link, as the two hospitals they were sampling had upped their use of hand sanitizers containing isopropanol, an alcohol compound, to ward off infections, around 2002. Johnson and Stinear's research team tested the bacteria they had gathered to to low levels of isopropanol in the lab.

The compound wiped out most of the bacteria in the samples from 1997 to 2004, but it killed only about a tenth as many in the samples from 2009 to 2015. The researchers concluded that the increased use of the sanitizers enabled initially small strains of alcohol-resistant bacteria to survive and replace their non-resistant predecessors.

"We have proposed here that the significant positive relationship between time and increasing alcohol tolerance is a response of the bacteria to increased exposure to alcohols in disinfectant preparations," the researchers wrote.


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