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Bacteria triumph again. Superbugs have found a way to alter their genes to make it harder to kill them with alcohol-based hand sanitisers.

Alcohol-based hand sanitisers were widely introduced to hospitals in the early 2000s to stop the spread of drug-resistant superbugs like methicillin-resistant听Staphylococcus aureus (MRSA) and vancomycin-resistant enterococcus (VRE) on people鈥檚 hands.

Although these bacteria had already evolved resistance to antibiotics, it was assumed they wouldn鈥檛 be able to do the same for alcohol. This is because alcohol kills them much faster by dissolving their outer membranes.

But now it appears that this assumption wasn鈥檛 quite right. Although hospital MRSA rates have sharply declined since hand sanitisers were introduced, VRE rates have increased . This is concerning because of infected patients do not survive.

Research led by at the University of Melbourne and at Austin Hospital suggests that VRE bacteria have developed alcohol tolerance.

Getting stronger

They used paper wipes soaked in alcohol-based hand sanitiser to disinfect mouse cages that had been coated with VRE samples from 1998 or 2012. The alcohol was 35 per cent less effective at killing the 2012 VRE bacteria, as determined by the proportion of mice that were infected when they subsequently entered the cages.

To understand how the Enterococcus bacteria developed this tolerance, they studied 139 samples collected from Melbourne hospitals between 1998 and 2015.

The more recent bacteria were found to be 10 times more tolerant to alcohol than the older ones, which seemed to correspond with changes in their alcohol-processing genes. These alterations may have made their membranes more impervious to alcohol.

It was probably na茂ve to think that superbugs wouldn鈥檛 be able to adapt to alcohol-based hand rubs, says at the University of Sydney. 鈥淚f you think about everything we鈥檝e ever introduced to try to combat bacteria, they鈥檝e always found a way to evolve and get around it,鈥� he says.

VRE may have built up more alcohol tolerance than MRSA because it is used to adapting to harsh conditions like the acidic regions of the gut, says Stinear.

The findings don鈥檛 necessarily show that alcohol-based hand rubs don鈥檛 work against VRE, but that healthcare workers may not be using them properly, says Grayson. If they sometimes forget to use them or use gel and foam formulations with lower alcohol contents, superbugs have a better chance of surviving and evolving tolerance, he says.

Regardless, it may be worth switching to hand sanitisers that contain alcohol and another antibacterial agent like chlorhexidine, so that there鈥檚 a second method of killing, Grayson says. Handwashing with soap is also useful for physically removing bacteria, he says.

O鈥橲ullivan agrees. 鈥淏ut it鈥檚 also a warning call that we need to be looking at developing new and better ways to disinfect our hands and the hospital environment.鈥�

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