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Name: Alfred
Status: other
Grade: other
Location: CA
Country: USA
Date: Spring 2011


Question:
I was wondering if there's a way I can kill every germ (including "super-bugs") on my hand? And if so, how I can do it? And if not, why not? One microbiologist said I can kill every germ on my hand, by lathering my hands in soap, rinsing them with warm water, re-lathering them in soap, rinsing them with warm water again, wiping them dry, and then rubbing them vigorously with hand sanitizer. I was wondering, is that really true?



Replies:
Alfred,

It's very hard to be sure you've killed *every* organism. It's quite possible that a single 'germ' could manage to stay alive and begin reproducing. In microbiology, a term known as "log kill" is used. This refers to the use of logarithms to describe what fraction of organisms have been killed. For example, if you kill 99% of the the organisms, you would have a fraction of 10^-2 left (0.01), which is referred to as "2 logs killed". If you are more aggressive, you might get "6 log kill" -- or 10^-6 left, which is 99.9999% killed. However, this scale never reaches zero -- in other words, there is still a chance that an organism remains alive no matter how aggressively you try to kill them all. There are very very aggressive ways to kill organisms that I would NOT recommend you try on your hands, but even those have a chance of leaving one or more behind alive. Also, it's very hard to detect single living organisms until they've had time to reproduce to a higher abundance -- so it's hard for you to know instantly if there are organisms alive on your hands or not.

It's true that washing your hands and using hand sanitizer will kill the vast majority of bacteria on your hands, but it would not be accurate to say it would kill "every single one of them". There's still a chance that one or more bacteria could remain alive. Also, some non-bacteria - such as spores, fungii, viruses, etc. may still remain as well. The "superbugs" to which you refer would mostly be killed by this process as well.

Hope this helps, Burr


Hi, That might help but cannot eliminate the bacteria completely. Alternatively, it can be achieved by usage of alcohol (100 or 70% Ethanol). Usually, in microbiology laboratories, before working on a laminar hood (aseptic environment) the hands are wiped with alcohol. A small experiment is performed by undergraduate students, where they are asked to place the thumb impression on a solid media plate with one thumb wiped with alcohol and the other without. After incubation period you would observe that, there would be no growth on the impression of alcohol sterilized thumb, whereas, the unsterilized thumb would show growth of bacteria. However, these are all temporary solution. You cannot live without bacteria ! Regards..

-- N.Arun Prasanna. ME (PhD)., Doctoral Student, IIT-Bombay, INDIA



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