Bacteria Evolves to Become Hand Sanitizer Resistant


A recent study reveals that bacteria can develop a tolerance to the alcohol used in hand sanitizers. This research focused on bacteria collected from two Australian hospitals from 1997 until 2015, which coincides with an increased usage of hand sanitizers based on alcohol.

Hand sanitizers might not be effective against some bacteria

A team of scientists from the University of Melbourne, led by microbiologist Timothy Stinear and infectious disease expert Paul Johnson, decided to conduct a research after they noticed that an increase in the usage of alcohol-based hand sanitizer in hospitals caused a significant decline of some species of bacteria, while others became even more active.

Enterococci bacteria, usually harmless inhabitants of the human gut, might sometimes become responsible for infections in hospitals. Amongst them, especially Enterococcus faecium shows signs of drug resistance, which made this species a perfect subject of study for the scientists.

The secret of the supernatural resistance of the bacteria

In order to find out what exactly lies behind Enterococcus faecium’s high survival rate, the researchers studied the samples taken from patients infected in two hospitals in Australia between 1997 and 2015. In the first part of the examination, the germs were treated with a mixture of water and 23 percent of isopropanol, a type of alcohol commonly used in hand sanitizers. The results clearly show that bacteria gathered before 2004 had much lower survival rate than those collected between 2009 and 2015. It has to be noted that the usage of hand sanitizer in hospitals began to significantly increase in 2002.

Enterococcus faecium becomes more and more infectious

In the second phase of the study, the resistant and non-resistant strains of the bacteria were spread on the floors of mouse cages, then a 70 percent alcohol solution was used to wash the surfaces. Once the cages were cleaned, the mice were placed in them for one hour. This experiment, which was repeated several times, showed that alcohol-resistant bacteria infected significantly more rodents than older and less resistant strains.

According to a genetic study, this alcohol tolerance seems to be caused by mutations of many genes that make E. faecium stronger. But how exactly this mechanism works we do not know yet. The scientists hope that future research will provide us with some more detailed explanations.


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