Science Questions

Are soaps and sanitisers breeding superbugs as well as antibiotics?

Sun, 12th Oct 2008

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Jeremy Mode asked:

Are soaps and sanitisers breeding superbugs as well as antibiotics?



Chris - No, they're not. The reason I would say that is because when we use soaps and things what the soap is actually doing is dislodging dirt, grease and effectively bacterial food from your hands as well as the bacteria themselves. This is assuming you're using them to get rid of bacteria. Your hands are a breeding ground for bacteria because they're covered in the vestiges of your last meal. They're covered in bits of you. They're covered in sweat. This is a bacterial banquet. If you come in with the soap what the soap does is to knock off all of that debris from places where bacteria could lurk making the hands much harder to provide a home for bacteria. It doesn't matter if the bacteria become resistant to the soap. What the soap is doing is making the hands into the equivalent of a Sahara desert instead of a bacterial oasis. That's why effectively washing your hands is good to get rid of bugs.

Kat - James also wants to know are soaps and sanitisers affecting our immune system? This theory that you need a certain amount of bugs and yuk to have a healthy immune system?

Chris - This is a huge can of worms. The answer is possibly but there's a concept called the “hygiene hypothesis.” This suggests that the immune system needs educating from a young age in order to tell the difference between friend and foe. The way it does that is by exposure to things in the environment that we need to know are friendly and the things that are not friendly. Some people suggest that non-exposure to the things that are both friendly and moderately nasty – if you don't let your immune system learn to recognise those then the immune system almost twiddles its thumbs and says well, if I'm not doing that then I might as well react to everything. You get this hyperactive immune system that reacts to things it should be ignoring. It's a possibility.


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Jeremy Mode asked the Naked Scientists:

What are the antimicrobials (soaps and sanitizers) doing to the evolution of the human immune system?

If we are killing off all the bacteria and viruses that would normally stimulate our immune system, what is stimulating the evolution of the immune system, in this supper sanitized society?  How deficient has the immune system become over the last 50 years and are we breeding superbugs using antimicrobials?

Is there any parallels to the misuse of the Antibiotics.

This is in response to the show on 9/22/2008

What do you think? jmode, Fri, 3rd Oct 2008

Well, it is important to understand that evolution does not occur with in a single individual but in populations over many generations. So there isn't really any worry about something pushing the evolution of the human immune system. Additionally, most of these bacteria are on the exterior of the human and so don't stimulate the immune system anyway (of course, the chance of them getting in is why we wash the hands anyway, so obviously it can happen). In general the immune system is either working or depressed. You can't really supercharge it or boost it in any way.

That said, the generations of bacteria are MUCH shorter, so the use of antimicrobials does indeed create a new environment that a bacteria that better fits the niche will out perform other bacteria that are hurt by the environment. So the potential is there for these antimicrobials to help "breed a super bug."

My guess though, with no factual data that I know of to back me up, is that the change in the environment on our hands is pretty minor overall. You touch on what I do think is a problem though... the misuse of antibiotics.

The issue isn't necessarily evolutionary (though that is there), but simply environmental. If you use a broad spectrum antibiotic it kills any suseptible bacteria and those that are less suseptible live to repopulate the now free niche that you created by killing off their competition. So, the need to use the antibiotic has to outweight the potential for harm it creates (really the rule of thumb for ANY medicine).

Sean Mahoney SeanMahoney, Tue, 14th Oct 2008

Actually, evolution does occur with a single individual.  It's just that it's only when the mutation in that individual confers an advantage over the other individuals and gets propagated through the species that we recognise that evolution has occurred.

Parallel evolution, where the same advantageous random mutation occurs in many individuals at the same time isn't actually impossible but the probability of it happening is so low that it approaches the impossible i.e. the odds of it occurring approaches 1:infinity. LeeE, Tue, 21st Oct 2008

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