Transcript Effects of household and commercial cleaning agents on

Effects of household cleaners on Escherichia coli
Brian Agee
Undergraduate Microbiology Major
Department of Biology
Tennessee Technological University
Cookeville, TN 38505
-Thousands of people develop illnesses
due to contact with Escherichia coli
everyday.
-Over the years, various disinfectants
have been developed claiming to
reduce the chances of coming into
contact with this bacterium. (Levy
2001)
-However, every year there are
numerous cases in which someone
becomes sick due to contact with
Escherichia coli. (Rusin 1998)
Results
Assay 1:Disc Diffusion Assay
60
Zone of Inhibition (mm)
Introduction
50
40
30
20
10
0
Clorox Germ-X
Bleach
Ajax
409
Lysol
Vinegar
Cleaning Agent
All cleaning agents that were tested were proven to
inhibit Escherichia coli. Clorox bleach was found to be
the best inhibitor, with a zone of inhibition 3-4 times
greater than any of the other cleaning agents.
Assay 2: Tube Growth Assay
Objective
The objective of my experiment is to
determine if Escherichia coli is
susceptible to common household
cleaners, and in the process determine
which cleaners are the most effective at
inhibiting and killing the bacteria.
Hypothesis
Escherichia coli will be susceptible to the
common household cleaners and therefore
will not be able to grow in their presence.
Cleaning Agent
Cloudiness (+/-)
Growth
(+/-)
None
+
+
Clorox
-
-
Clorox (50%)
-
-
Germ-X
-
-
Germ-X (50%)
-
-
Ajax
-
-
Ajax (50%)
-
-
409
-
-
409 (50%)
-
-
Lysol
-
-
Lysol (50%)
-
-
Vinegar
-
-
Vinegar (50%)
-
-
- All cleaning
agents were
effective at
killing
Escherichia coli,
even when
reduced by 50%
concentration.
- The only growth
occurred where
the control,
which consisted
of nutrient broth
and Escherichia
coli, was
streaked.
Methods and Materials
Two assays were used to determine the cleaning agents
effectiveness against Escherichia coli. The procedure for
both assays was performed according to that of Dr. Susan
Goss. (Goss 2005)
Assay 1: Disc Diffusion Assay
- Determines the effectiveness of the cleaning agent at
inhibiting Escherichia coli.
- Each cleaning agent was applied to a disc and placed on
a TSA plate with Escherichia coli.
- TSA plates were then incubated for 48 hours at 35.6°C.
- After the 48 hour incubation, the zone of inhibition was
measured in millimeters.
Assay 2: Tube Growth Assay
- Determines the effectiveness of the cleaning agent as a
bactericidal agent.
- Escherichia coli was placed into a test tube with each of
the cleaning agents and incubated for 48 hours at 35.6°C.
- Samples from each test tube were streaked on TSA
plates and also placed in the incubators for a period of 48
hours.
- If growth occurred on the TSA plate, then the cleaning
agent was ineffective at killing Escherichia coli.
Conclusions
As hypothesized, Escherichia coli was susceptible
and did not survive in the presence of all of the
cleaning agents. The most effective cleaning agent
proved to be Clorox bleach, which had a zone of
inhibition 3-4 times larger than any other cleaning
agent tested. In order to keep our society healthy,
cleaning agents must be used on a daily basis to
prevent the spread of bacteria.
Acknowledgements
I would like to acknowledge Dr. Susan Goss, Professor of
Biology at Tennessee Technological University for
allowing me to use the Microbiology Laboratory and
for all of the assistance that she provided.