Even high-strength hospital disinfectant is losing its effectiveness against superbugs, scientists have warned, with bacteria learning to adapt to survive in the face of alcohol-based hand sanitisers.

It's the alcohol in particular that the bugs are becoming more resistant too, according to new research, which looked specifically at the Enterococcus faecium bacteria – one of the leading causes of infections in hospitals.

A particular group of bacteria, known as vancomycin resistant enterococci (VRE), seems to have mutated to prevent alcohol from busting it into oblivion. While it's not time to ditch sanitizer yet, the researchers say, it is time for a rethink.

"This isn't the end of hospital hand hygiene, that's been one of the most effective infection control procedures that we've introduced worldwide," says one of the team, molecular microbiologist Tim Stinear from the Peter Doherty Institute in Australia. "The WHO recommends it."

"But we can't rely solely on alcohol-based disinfectants and for some bacteria, like VRE, we're going to need additional procedures and policies in place. For hospital this will be super-cleaning regimens, which include alternative disinfectants, maybe chlorine-based."

The researchers tested a total of 139 samples of E. faecium taken from patients before and after the widespread adoption of alcohol-based hand sanitiser in Australian hospitals, covering a period from 1997 to 2015.

After these samples were exposed to an disinfecting alcohol solution, it was found that the bacteria collected after 2010 were some ten times more tolerant to the substance.

In further tests, some of the bacteria samples were applied to mice cages, then cleaned up using hospital-strength sanitising wipes. 

The mice that were put in a cage with a 2012 strain of E. faecium showed more of it in their poop - a clear indication that the alcohol was not as effective compared to the earlier strains. The later strains of bacteria were proving to be more resistant.

"It shows that it is not just a laboratory phenomenon that we are measuring here," Stinear told Nicola Davis at the Guardian. "We are showing this characteristic [of the bacteria] transfers into being able to escape a standard infection control procedure."

Additional genetic analysis of the bacteria resistant to alcohol revealed that they had developed mutations in specific genes linked to cell metabolism. However, the resistance to alcohol seemed to have a different genetic basis than the bacteria's resistance to antibiotics in general.

The VRE group of bacteria are particularly dangerous to patients who've had a course of antibiotics that has disrupted the normal composition of their gut bacteria. In other words, some of the people who are the most sick in hospital are the most at risk.

VRE bugs can go on to cause infections in the urinary tract, wounds, and the bloodstream, and they're already resistant to several classes of antibiotics.

What needs to happen next is more research: further studies that cover more hospitals, more countries, and more strains of bacteria, and studies which try to establish a definitive link between the increased tolerance of E. faecium and the introduction of hand sanitiser in hospitals.

In the meantime, it's important to note that alcohol rubs have been effective in many ways, including cutting rates of MRSA infections in hospitals – these disinfectants essentially blow away the membranes of bacteria cells to kill them off.

But these hand rubs might need to be used in combination with other procedures, the researchers say, and should always be used correctly. People's unwillingness to clean their hands for a full 20-30 seconds, as is recommended, could be one of the reasons why this bacteria has had a chance to mutate and become resistant.

The researchers suggest that as well as longer periods of hand-washing, hand sanitisers with a higher percentage of alcohol and more efficient patient isolation might also help. We should also be looking at more comprehensive cleaning regimes, they say.

"An extra level of infection control, that doesn't just rely on alcohol-based disinfectants is required," says Stinear.

The research has been published in Science Translational Medicine.