October 1, 2018

Hand sanitizers—long a 'sledgehammer' against bacteria—may be losing their effectiveness

Daily Briefing

    In recent years, hospitals around the world have adopted alcohol-based hand-sanitizer to prevent the spread of infections, but a new study suggests at least one type of multidrug-resistant bacteria is growing more tolerant of the popular disinfectant.

    Learn how we can help you improve hand hygiene and cut infection rates to zero

    Measuring the resistance of a common hospital bacteria

    For the study published recently in Science Translation Medicine, the researchers looked at alcohol disinfectant tolerance in Eterococcus faecium (E. faecium) bacteria, a multidrug-resistant bacterium that can affect the digestive tract as well as other parts of the body, such as the bladder and heart. According to the researchers, E. faecium infections in health care settings have increased over the same time period hand sanitizer use has risen.

    The study involved 139 samples of E. faecium bacteria, which researchers collected from two hospitals in Melbourne, Australia, between 1997 and 2015.

    The researchers tested the bacteria's tolerance to different strengths of alcohol, starting at 23%. Hand-sanitizers are typically 60% alcohol, according to NPR's "Shots."

    Bacteria is 'more tolerant' of hand sanitizer

    The researchers found while E. faecium is not resistant to alcohol, it is growing "more tolerant of it." Specifically, the bacteria that were obtained after 2009 were 10 times more tolerant of the alcohol solution than the bacteria collected before 2004. 

    The researchers found a solution with a 70% alcohol concentration was needed to "conque[r]" all the bacteria, Scheiber reports.

    The researchers found that the E. faecium samples that were more tolerant to alcohol had "accumulated mutations in genes involved in carbohydrate uptake and metabolism."

    Hand washing might be the response to 'innovative organisms'

    According to researchers, the study results might help explain why the rate of E. faecium infection continues to grow in hospitals worldwide, despite the increased use of hand sanitizer.

    "To our knowledge this was the first time anyone had shown hospital bacteria becoming tolerant to alcohols," Timothy Stinear, a co-author of the study and researcher at the University of Melbourne's Doherty Institute for Infection and Immunity, said.

    The findings took several experts by surprise.

    Lance Price, a professor at the George Washington University's Milken Institute School of Public Health, said, "I always thought of alcohol as being like a sledgehammer." He added, "But clearly, these are innovative organisms ... evolution happens pretty fast when you're dealing with populations that can double every 30 minutes and travel in packs of billions."

    To control the spread of alcohol-tolerant bacteria, hospitals will have to "adhere rigorously to hand-hygiene protocols," Stinear said.

    Price said, "If you're washing your hands less because that alcohol-based hand sanitizer makes you feel confident that your hands are clean, all of a sudden you can become a vehicle for alcohol-resistant organisms," such as E. faecium and Clostridium difficile (C. diff). He added, "We have to be careful about this new trend towards heavy reliance on alcohol-based hand sanitizers. Soap and water should be our number-one protection" (Schreiber, NPR, 8/2; Rettner, Live Science, 8/3; Vaidya, Becker's Hospital Review, 8/2; Pidot et al., Science Translational Medicine, 8/1).

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