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
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
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.
Click here to return to the Molecular Biology Archives
Update: June 2012