Naked Science Forum
Life Sciences => Cells, Microbes & Viruses => Topic started by: moses lawn on 05/12/2004 15:29:16
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Many public places are replacing bars of soap in their washrooms with "antibacterial" handwash dispensers.
While it makes good sense not to use bars of soap to pass contamination from one person to another, yet just how effective are these handwash liquids that are claimed to be antibacterial?
Do they really reduce bacterial contamination to a greater degree than ordinary liquid soaps? And just how longlasting is their effect? Do hands washed with them carry some continuing antibacterial properties, or are they re-infected with the first contaminated surface they touch after the wash?
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The following might not really contain an answer to your question, but it is associated.
When I was a biology student we performed an experiment that tested different soaps and alcohol for desinfection. Toiletpaper was tested as well. It was a simple experiment that used petridishes with sterile solid medium and petridishes with a marker strain, Serratia marcesens, a good marker because of its red colonies.
Of course we ample hands available. First we needed to press our left and right hand on a sterile petridish, separate dishes. Then take 1, 2, 3, 4, 5, 6, 7 or 8 layers of toilet paper and push your left hand with the paper in between on the plate with serratia (so to check how many layers you need before no bacteria would go through). Then press both hands on fresh sterile plates again. Then the pairs of hands washed only water or with soap or with antibacterial soap. Press both hands on petridish. Then 1 or 5 minutes in a layer of alcohol. And again on a fresh steril petridish. Make sure to label everything well! Petridishes where incubated overnight and analysed the next day.
Results:
You need a couple of layers before hardly any bacteria arrive at your hands. So washing your hands is a good hygenic thing to do. But while washing you infect your other hand as well. There were minor differences among the use of water, normal soap or antibacterial soap, with the soaps removing more bacteria. Drying hands was a definite major improvement (sorry not mentioned above, but this step was included as well). Also alcohol killed of the bugs very nicely.
Conclusion:
If you want to save the rainforest and do not want to use a whole tree to wipe of your ass then wash your hands with water or mild soap and dry thoroughly. The indigenous microflora on your hands protect against evil invaders. Cleaning your hands to rigourously also kills them of, making your hands prone to investation with them evildo-ers.
--- man is twice the worm it used to be ---
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What I find remarkable about public toilet facilities is that repeatedly the doors are arranged so that you can push them on your way in, but on your way out, you need to use the handle.
Now let's be honest about this. When are people most likely to have dirty hands - on the way in, or on the way out ?
Toilets should be set up so that you can push open the door - with an elbow, or even your foot, when leaving so that, having just washed your hands, you then do not have to touch the door handle - which someone who has not washed their hands, and is suffering from, say, diarrhoea, has just touched and contaminated with campylobacter or salmonella, or E. coli.
Washing your hands is actually a very good way to add bacteria to them. In old facilities where you need to touch the taps you merely reinfect yourself from the taps having just assiduously scrubbed your skin clean, and add a few bugs that other people left there too. But most of them are harmless.
Indeed, most people, most of the time, are a seething mass of bacteria. In fact, there are more bacterial cells in and on you than there are cells 'of' you.
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Chris..I soooooooooo agree with you about the public toilets....I try and grab the handle at the bottom, where I hope most people don't touch it....and if I can I use a piece of tissue to hold as a barrier. It absolutely galls me how many people do not wash their hands after going to the loo.
Duncan...what a brilliant experiment...I found your answer very interesting...thanks
'Men are the same as women...just inside out !'
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Yep, I always hold on to the towel I dried with and use it to open the door. Probably I should use a dry towel instead. Want to hear something worse? When I took an infection control class they told me that the highest concentration of urine in a public restaurant, besides the bathroom, was at the toothpick container. Haven't used a "public" toothpick since. Yuck!
On the handwashing issue, I remember reading an article once that said the type of soap you use isn't very important. The actual friction of washing is what removes the germs more that the soap.
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quote:
Originally posted by bezoar
On the handwashing issue, I remember reading an article once that said the type of soap you use isn't very important. The actual friction of washing is what removes the germs more that the soap.
Perhaps that's why those oval metal things are good too..I can't remember what they are made of...I think it may just be stainless steel. in fact, come to think of it, I'm sure I posted a question about them once......and I will never ever use a public avaialable toothpick again....thanks Nursey[:)]
'Men are the same as women...just inside out !'
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Thanks to everyone for their most interesting responses.
So it seems that the antibacterial content of liquid soaps is just an expensive irrelevance, more to do with marketing than hygeine.
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You can find out on this week's radio show because we're discussing bacteria including superbugs and novel ways to get rid of them including Phage therapy, and other predatory bacteria (Bdellovibrio)....
TNS
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Chris,
Have you, or are you planning any discussion of community acquired MRSA?
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quote:
Originally posted by neilep
quote:
Originally posted by bezoar
On the handwashing issue, I remember reading an article once that said the type of soap you use isn't very important. The actual friction of washing is what removes the germs more that the soap.
Perhaps that's why those oval metal things are good too..I can't remember what they are made of...I think it may just be stainless steel. in fact, come to think of it, I'm sure I posted a question about them once......and I will never ever use a public avaialable toothpick again....thanks Nursey[:)]
'Men are the same as women...just inside out !'
Stainless steel is toxic to most microorganisms. This is why food service (in the states anyway) require most surfaces and cooking utensils be stainles steel.
The ingredient in most antibacterial soaps is triclosan. It's pretty effective in killing off certain types of bacteria but you need a VERY thorough washing. We tested triclosan along with many other common supposedly anti-bacterial household cleaners and it was among the more effective. You really need to scrub into the nooks and crannies of your fingers and hands though or you won't get it in the required concentration to be toxic to them.
This message brought to you by The Council of People Who Are Sick of Seeing More People
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This week's show (that went out yesterday) was all about MRSA in hospitals and in the community. We also talked about phage therapy and 'living antibiotics' - predatory bacteria that seek out and destroy other infecting organisms...
http://www.thenakedscientists.com/listen
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
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Thanks Chris, I'll have a listen.