[atomic77]

> The researchers used different strengths of alcohol concentrations to combat the bacteria, starting with 23 percent. Eventually, at a 70-percent alcohol mixture, the bacteria were conquered. Typically, hand sanitizers are 60 percent alcohol.

Is it simply a matter of using higher concentrations of alcohol? Or is it possible that bacteria could evolve resistance right up to 100%?

[notanote]

A 70% solution is considered the most effective. Higher concentrations of alcohol (over 90% especially) evaporate more quickly, reducing contact time. Also, they work too quickly. By coagulating the outer proteins of bacteria instantly, they form a protective layer that actually stops the alcohol from penetrating further.

[mmt]

Although I agree that over 90% is less effective (and your explanation is clearer than mine [1]), do you have a reference for 70% (and is it w/w or v/v?) is the most effective?

Last I read up on it, I found the number to be closer to the European hospital standard of 85%, although I don't have the reference in my bookmarks, nor do I recall if it was reflect of scientific consensus, if one even exists on the topic.

[1] https://news.ycombinator.com/item?id=17684070

[ars]

> Or is it possible that bacteria could evolve resistance right up to 100%?

Adding some water to alcohol kills more bacteria than pure alcohol.

See here: https://blog.gotopac.com/2017/05/15/why-is-70-isopropyl-alco...

[hcurtiss]

It’s not like an antibiotic. At sufficient concentrations, it seems like the lipids in the cell membrane would simply dissolve.

[Fomite]

One of the problems with alcohol-based hand sanitizers is that there's a war between "Kills Bacteria" and "Demolishes Your Hands" - one of the major problems in hospitals is compliance, and the harsher the alcohol concentration, the harder it is to get people to use it.