Hand-sanitizer resistant bacteria strains are developing

How worried should we be about bacteria with an alcohol tolerance? Be afraid, be very afraid.

One of the few things that we can be sure of is that every action is likely to have an unintended consequence. While on a daily basis these side-effects can be annoying at worst or convenient at best, at institutional scales they can be dire. In some cases, they can be deadly.


A new study published in Science Translational Medicine on the effects of hygiene practices in Australian hospitals gives us an excellent example of this, showing us how a wonderful program can have disastrous side effects.

What was the program? How did it foul up? 

In 2002, Australian hospitals introduced new procedures to help cut down on MRSA infections which included hand washing with alcohol-based hand sanitizers before and after interactions with patients. 

The hand sanitizer had the intended effect—new MRSA infections have been dropping for 15 years—however, study co-author Paul Johnson noticed that the decline in MRSA infections had been accompanied by a slow rise in Enterococcus faecium infections. He suggested that perhaps the bacteria were evolving tolerance to the alcohol-based sanitizers.

While the idea seemed far-fetched, an experiment was devised to confirm or deny the hypothesis.

What did the experiment show? 

139 cultures of Enterococcal bacteria, a microbe that usually lives in our guts but can cause dangerous infections and even sepsis if it gets anywhere else, taken from Australian hospitals at different points over the last several years were treated with an alcohol solution similar to that used in common hand sanitizers.

As hypothesized, the newer strains showed more tolerance to the solution than the older ones did, demonstrating that the strain has evolved a higher tolerance to being smothered with alcohol over time.

The alcohol-tolerant bacteria were also found to be capable of living in the guts of mice living in an environment that was cleaned with alcohol, showing that the tolerance wasn’t a fluke limited to a petri dish.


Somehow, this isn't even the scariest experiment involving mice we know about. (SAM YEH/AFP/Getty Images)

Wait, what? Is this even possible? 

That was the exact reaction of co-author Tim Stinear. Ethyl alcohol kills germs in a very gruesome fashion, literally dissolving the lipids that hold the cell together while simultaneously preventing vital cellular functions from occurring. It would be like a person going into a vat of battery acid.

Bacteria that can tolerate this for extended lengths of time before dying boggle the mind.

Reflecting on the idea that inspired the study, professor Stinear recalled, “Paul (Johnson) said ‘maybe they’re becoming tolerant to all the alcohols we use in our hand hygiene products’ and we said, ‘that’s ridiculous. What are the chances that something could become tolerant to alcohol?’”

You know something’s wrong when a doctor thought that what’s happening was too absurd to consider.  

How did it happen? 

The effectiveness of hand sanitizers is dependent on proper usage. The WHO recommends that people rub sanitizer on their hands for 20-30 seconds, but of course, not everybody does that. Using any antimicrobial agent at a subtherapeutic level can lead to bacterial immunity and is a leading cause of antibiotic resistance.

Essentially, bacteria that weren’t killed by the alcohol rubs, either because they were exposed for just too little time or they had a natural mutation that gave them some protection, were able to survive and multiply while those that were killed off did not. Natural selection took its course.

How bad is this? 

Extremely bad, if the current trend continues.

Some strains of Enterococcus faecium are already resistant to last-line antibiotics, meaning that they are challenging to treat when an infection occurs. If they were to become more tolerant than they are to the hand sanitizers used in hospitals, then we could easily see a scenario where entire hospital wards are shut down to try to contain outbreaks of a disease that can neither be readily treated or prevented. Such things have happened before over MRSA infections.

The hospital environment—filled with people who are already ill and extra vulnerable to such a disease—would inflate the death toll from such an outbreak.

Is there any good news? 

Yes, there is.

Firstly, the bacteria still die when placed in higher concentrations of alcohol. However, this is stronger than many hand sanitizers used at hospitals. It does suggest that we aren’t quite doomed yet.

Secondly, this tolerance to alcoholic sanitizers doesn’t extend to other hygiene practices. Handwashing, which doesn’t kill bacteria so much as it lifts them off your hands and flushes them down the drain, is still effective against pretty much everything, but don’t be taken in by the notion that antibiotic soaps are of much use

The measures introduced in Australia to reduce MRSA infections in hospitals were largely successful but had the side effect of increasing the number of Enterococcus faecium infections. If left unchecked, this new problem could prove deadlier than the last one. 

While we don’t have to worry about an apocalyptic pandemic just yet, this story should remind us that we can’t fully control our environments and that even well-enacted plans with the best of intentions can have horrible results on the side.  

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Researchers at the University of Colorado Boulder found that the fatty 10(Z)-hexadecenoic acid from the soil-residing bacterium Mycobacterium vaccae aids immune cells in blocking pathways that increase inflammation and the ability to combat stress.

The study's senior author and Integrative Physiology Professor Christopher Lowry described this fat as "one of the main ingredients" in the "special sauce" that causes the beneficial effects of the bacterium.

The finding goes hand in hand with the "hygiene hypothesis," initially proposed in 1989 by the British scientist David Strachan. He maintained that our generally sterile modern world prevents children from being exposed to certain microorganisms, resulting in compromised immune systems and greater incidences of asthma and allergies.

Contemporary research fine-tuned the hypothesis, finding that not interacting with so-called "old friends" or helpful microbes in the soil and the environment, rather than the ones that cause illnesses, is what's detrimental. In particular, our mental health could be at stake.

"The idea is that as humans have moved away from farms and an agricultural or hunter-gatherer existence into cities, we have lost contact with organisms that served to regulate our immune system and suppress inappropriate inflammation," explained Lowry. "That has put us at higher risk for inflammatory disease and stress-related psychiatric disorders."

University of Colorado Boulder

Christopher Lowry

This is not the first study on the subject from Lowry, who published previous work showing the connection between being exposed to healthy bacteria and mental health. He found that being raised with animals and dust in a rural environment helps children develop more stress-proof immune systems. Such kids were also likely to be less at risk for mental illnesses than people living in the city without pets.

Lowry's other work also pointed out that the soil-based bacterium Mycobacterium vaccae acts like an antidepressant when injected into rodents. It alters their behavior and has lasting anti-inflammatory effects on the brain, according to the press release from the University of Colorado Boulder. Prolonged inflammation can lead to such stress-related disorders as PTSD.

The new study from Lowry and his team identified why that worked by pinpointing the specific fatty acid responsible. They showed that when the 10(Z)-hexadecenoic acid gets into cells, it works like a lock, attaching itself to the peroxisome proliferator-activated receptor (PPAR). This allows it to block a number of key pathways responsible for inflammation. Pre-treating the cells with the acid (or lipid) made them withstand inflammation better.

Lowry thinks this understanding can lead to creating a "stress vaccine" that can be given to people in high-stress jobs, like first responders or soldiers. The vaccine can prevent the psychological effects of stress.

What's more, this friendly bacterium is not the only potentially helpful organism we can find in soil.

"This is just one strain of one species of one type of bacterium that is found in the soil but there are millions of other strains in soils," said Lowry. "We are just beginning to see the tip of the iceberg in terms of identifying the mechanisms through which they have evolved to keep us healthy. It should inspire awe in all of us."

Check out the study published in the journal Psychopharmacology.