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Name: Saurabh
Status: Other
Grade:  Other
Location: N/A
Country: United States
Date: August 2005

How does one go about ascertaining whether a particular liquid/chemical is an antiseptic and/or a disinfectant?

The distinction between disinfectant and antiseptic is not clear; both tend to kill and/or inhibit the growth of micro-organisms. To test if they are capable of killing bacteria, take a culture of E. coli (~10e+9/mL), for example, and dilute it 1:100 into the liquid agent you are testing. Let it "incubate" for 60 min and then dilute the suspension 1:10,000 into saline solution. Then spread 0.1 mL of the 1:10,000 dilution on an agar plate that will support the growth of E. coli. If there is no antiseptic effect, you should see approximately 100 colonies after incubating the plate. If you observe significantly less than 100 colonies, there is an antiseptic effect. The negative control for this experiment is to dilute the bacterial culture 1:100 into saline solution and dilute and plate the same as the test samples.

Good luck!

Ron Baker, Ph.D.

This is not easy. An antiseptic/disinfectant is a substance that kills some sort of micro-organism. It depends upon many conditions: the type(s) of microbe (virus, bacterium, parasite, etc.), the environment (internal to the body, wet surface, dry surface, air, temperature, pH, etc.), and a lot of other conditions. There are some substances such as chlorine bleach and regular soap that have a fairly wide spectrum of microbial activity, but even those are not "universal". It is difficult to make generalizations though.

Vince Calder

Antiseptics are antimicrobial agents that are used on living tissue. Examples are alcohol, hydrogen peroxide, Bactine, etc. Disinfectants are usually stronger or more toxic to living tissue. Examples are bleach and some chemicals. Sometimes a disinfectant can be diluted until it can be used as an antiseptic.


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