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  • [ ♪INTRO ]

  • You've probably heard of superbugs: infectious

  • microbes that become resistant to our most effective treatments.

  • So with the COVID-19 pandemic, when the whole world became obsessed with alcohol-based hand

  • sanitizers, you might have started to wonder whether using too much of them could make

  • the superbug problem worse.

  • But, as far as researchers can tell, that's not really a concern.

  • And that's because alcohols chemically attack molecules that are fundamental to all cells.

  • Bacteria generally can find ways to resist antibiotics because these drugs use focused

  • strategies to kill or hinder those microbes.

  • Like, they block the action of one protein or something.

  • But if the bacteria tweak that protein bit, or find a way to get rid of the antibiotic

  • itself quickly, then the drug won't work.

  • Alcohol-based hand sanitizer is different because it messes with a lot of things.

  • They usually contain isopropanol the same stuff as rubbing alcohol and/or ethanol, the

  • alcohol found in booze.

  • Both of these rip cells open and destroy the proteins inside.

  • See, cells are surrounded by a membrane: a double layer of fatty molecules which keeps

  • their insides in and their outsides out.

  • But ethanol and isopropanol are teeny.

  • They are almost nothing compared to them.

  • Just two or three carbon atoms, a hydroxyl group, and some hydrogens.

  • And, in part because of that, they can slip their way in between the membrane's layers.

  • There, they mess with the fatty molecules a bit, ultimately making the barrier more porous.

  • This may be damaging enough on its own, as cells with weakened membranes tend to leak

  • important things, or get over-filled with water.

  • But also, it lets lots of alcohol get fully inside the cell, where it wreaks havoc on

  • the proteins that keep the microbe functioning.

  • And not just, like, one protein, like an antibiotic would.

  • These alcohols can react with different parts of many proteins, disrupting the bonds that

  • hold them together, and ultimately breaking them down in a process known as denaturation.

  • This is actually a major reason why the concentration of alcohol in hand sanitizer is so important.

  • Below sixty percent or so, and it can't destroy the microbe effectively.

  • But, you don't want to go overboard, either.

  • Ninety percent is usually the recommended maximum, because water helps speed up the

  • reactions between alcohols and proteins.

  • In the right concentration, these alcohols can kill most bacteria, although there are

  • some holdouts - namely, the few that can hunker down in tough structures called endospores.

  • Hand sanitizers can even destroy viruses that have a fatty outer layer, like coronaviruses, for similar reasons.

  • And becoming fully resistant to this level of destruction would involve much more than just a couple random mutations.

  • The microbe would have to change fundamental parts of its structure - like, suddenly develop

  • the ability to create endospores.

  • And scientists don't think that's very likely to happen.

  • Now, one study published in Science Translational Medicine in 2018 did find that a species

  • of bacteria was becoming more tolerant of the alcohol in hand sanitizers.

  • That led to a whole bunch of headlines about how microbes were becoming resistant to alcohol

  • and maybe we shouldn't use it anymore.

  • But that's not what the study's authors actually said.

  • The microbes increasing in prevalence were tolerant of about twenty-three percent alcohol.

  • They did not claim - and still don't - that microbes able to withstand seventy percent alcohol had evolved.

  • Rather, their concern was that improper use of sanitizers or unreliable formulations could

  • mean dangerous bacteria aren't exposed to high enough concentrations of alcohol, or

  • aren't exposed for long enough to fully kill them.

  • And that may mean hospital staff may believe surfaces are sterile when they actually aren't.

  • In fact, they stressed that people should continue using alcohol-based sanitizers, as

  • they save millions of lives every year.

  • They just urged more careful review of the products and protocols.

  • The point is, as far as we can tell, using alcohol-based hand sanitizer is not creating superbugs.

  • So go forth and sanitize!

  • Thanks to Paul, Fred, and Lorraine for asking us about hand sanitizers, and to everyone else who supports us on Patreon!

  • If you're a patron and you've got questions about how the world works, be sure to make good use of that QQ inbox.

  • We love hearing what you're curious about, and hey you might just get your questions answered in an episode!

  • And if you're not a patron, you can learn more about how to become one at Patreon.com/SciShow.

  • [ ♪OUTRO ]

[ ♪INTRO ]

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洗手液會不會產生超級細菌? (Does Hand Sanitizer Create Superbugs?)

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    林宜悉 發佈於 2021 年 01 月 14 日
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