Dangerous Bacteria Developing Resistance to Alcohol

A new study reports that Enterococcus faecium, a leading cause of hospital-acquired infections (HAIs) and already resistant to most antibiotics, is now developing resistance to common alcohol-based hand gels.

Researchers at the University of Melbourne (Melbourne, Australia), Murdoch University (Perth, Australia), and other institutions conducted a study to test the alcohol tolerance of 139 hospital isolates of E. faecium obtained between 1997 and 2015. They found that isolates collected after 2010 were 10-fold more tolerant to killing by alcohol than were the older isolates. Using a mouse gut colonization model, they showed that alcohol-tolerant E. faecium resisted standard 70% isopropanol surface disinfection.

They then looked for bacterial genomic signatures indicating adaptation to alcohol. The results revealed that alcohol-tolerant E. faecium accumulated mutations in genes involved in carbohydrate uptake and metabolism; subsequent mutagenesis confirmed the roles of these genes in the developing tolerance of E. faecium to isopropanol by making the cellular membrane more resistant to solvents. The researchers suggest that the bacterial adaptation necessitates implementation of new infection control procedures and protocols. The study was published on August 1, 2018, in Science Translational Medicine.

“E. faecium appears to be developing resistance to alcohol-based sanitizers, possibly in response to the vast use of the antimicrobial gels in hospital hand-hygiene programs; use has increased 10-fold over the past 20 years in Australian hospitals,” said senior author molecular microbiologist Timothy Stinear, PhD, of the University of Melbourne. “E. faecium has adapted to the health-care environment. It's a WHO and CDC-recognized superbug; in the hospital it is already resistant to nearly all classes of antibiotics.”

Washing hands with soap and water is still the best way to reduce the number of microbes on them in most situations. If soap and water are not available, an alcohol-based hand sanitizer containing at least 60% alcohol should be used at the point of care. But many people use hand sanitizers on soiled hands, may not use a large enough volume, or may wipe it off before it has dried. In addition, hand sanitizers might not remove harmful chemicals, such as pesticides and heavy metals. In most instances, therefore, soap and water are more effective than hand sanitizers at removing or inactivating certain kinds of germs.

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University of Melbourne
Murdoch University