Transcript Effects of household cleaners on Escherichia coli

Effects of household
cleaners on Escherichia
coli
Presented by:
Brian Agee
Undergraduate Microbiology Major
Tennessee Technological University
Cookeville, TN 38505
Introduction

“An increase in food-borne illnesses has
been observed in many countries recently,
with a high proportion of these outbreaks
occurring in the home.” (Rusin 1998)
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The most notable area where bacteria were
found was in the kitchen, where large
numbers of Escherichia coli was found.
(Josephson 1997)
Introduction
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Recent outbreaks of Escherichia coli have brought the
issues of hygiene and disinfection to the public’s
attention. (Cogan 2002)
Because of public attention, antibacterial agents
marketed for the home have increased from only a
few dozen in the mid-1990s to more than 700 today.
(Levy 2001)
In order to determine the efficiency of these
antibacterial products, their use in a household setting
must be considered. (Kusumaningrum 2002)
Introduction

Objective: Determine if Escherichia coli is
susceptible to common household cleaners and
which cleaners are the most effective at inhibiting
and killing the bacteria.

Hypothesis: Escherichia coli will be susceptible to all
of the cleaning agents and therefore will not be able
to survive in their presence.

Null Hypothesis: Escherichia coli will not be
susceptible to all of the cleaning agents and
therefore grow in their presence.
Methods and Materials
Assay 1: Disc Diffusion Assay (Goss 2005)
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Determines the effectiveness of the
cleaning agent at inhibiting Escherichia coli.
Cleaning agents used for this assay
included Clorox bleach, Ajax, vinegar,
Germ-X, Lysol, and 409.
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.
As the size of the zone of inhibition
increased, so did the cleaning agents
ability to inhibit Escherichia coli.
Methods and Materials
Assay 2: Tube Growth Assay (Goss 2005)
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Determines the effectiveness of the cleaning agent as a
bactericidal agent.
Cleaning agents used for this assay included Clorox bleach,
Ajax, vinegar, Germ-X, Lysol, and 409.
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.
Results
Assay 1: Disc Diffusion Assay (Goss 2005)
Table 1: Zones of Inhibition for common household cleaning agents.
Cleaning Agent
Zone of Inhibition (+ or -)
Size of Zone of Inhibition
(mm)
Clorox Bleach
+
60
Germ-X
+
13
Ajax
+
25
409
+
15
Lysol
+
20
Vinegar
+
15
Average Zone of Inhibition for Common
Household Cleaners
25
Results
Zone of Inhibition (mm)
Assay 1: Disc Diffusion Assay (Goss 2005)
60
50
40
30
20
10
0
Clorox Germ-X
Bleach
Ajax
409
Lysol
Vinegar
Cleaning Agent
Figure 1: Zones of inhibition against Escherichia coli for household cleaning agents
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Of the six cleaning agents tested, Clorox bleach was determined to be the best at
inhibitor of Escherichia coli.
The zone of inhibition of Clorox bleach was approximately 3-4 times larger than
any of the other cleaning agents. (Figure 1)
The average zone of inhibition for all of the cleaning agents tested was 25mm.
(Table 1)
Results
Assay 2: Tube Growth Assay (Goss 2005)
Table 2: Results from tube growth assay, which determined the effectiveness of
the cleaning agents at killing Escherichia coli
Cleaning Agent
Cloudiness in Test Tube (+ or -)
Growth on TSA Plate (+ or -)
None (Broth+Bacteria)
+
+
Clorox Bleach
-
-
Clorox Bleach (50%)
-
-
Germ-X
-
-
Germ-X (50%)
-
-
Ajax
-
-
Ajax (50%)
-
-
409
-
-
409 (50%)
-
-
Lysol
-
-
Lysol (50%)
-
-
Vinegar
-
-
Vinegar (50%)
-
-
Results
Assay 2: Tube Growth Assay (Goss 2005)
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All cleaners were effective
at killing Escherichia coli,
even when reduced to 50%
concentration. (Table 2)
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The only growth occurred
where the control, which
consisted of nutrient broth
and Escherichia coli, was
streaked. (Table 2)
Discussion
The main cause of the spreading of Escherichia
coli is primarily the result of poor hand and
surface hygiene. (Cogan 2002)
 According to Tsai, sodium hypochlorite
cleaners are effective at inhibiting and killing
surface germs. (Tsai 1999)
 The findings from my research seem to agree
with these previous findings because Clorox
bleach, a hypochlorite cleaner, was discovered
to be the most effective at inhibiting and killing
Escherichia coli.
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Discussion
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The main purpose of cleaning agents is to prevent
transmission of disease causing microorganisms. (Levy
2001)
Disinfection products used in combination with a regular
cleaning schedule can greatly reduce the amount of bacteria
found in the household. (Rusin 1998)
In a study conducted by Cole, he found that more target
bacteria are found in homes that don’t use antibacterial
products than homes that use these products. (Cole 2003)
These previous studies seem to agree with my research
because all of the cleaners tested seemed to inhibit and kill
the bacterium tested.
Conclusion
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Hypothesis: Escherichia coli will be susceptible to all of
the cleaning agents and therefore will not be able to
survive in their presence.
Null Hypothesis: Escherichia coli will not be
susceptible to all of the cleaning agents and therefore
grow in their presence.
My hypothesis was confirmed because Escherichia
coli was susceptible to all of the cleaning agents and
was not able to survive in their presence.
Therefore, my null hypothesis was rejected.
Conclusion
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All cleaning agents that were tested were proven to
be effective at inhibiting and killing Escherichia coli.
Clorox bleach was found to be the most effective
cleaning agent, producing a zone of inhibition
approximately 3-4 times greater than any of the
other cleaning agents tested.
In order to keep our society healthy, household
cleaners must be used on a regular basis in order to
help eliminate the chances of becoming infected by
a bacterium, especially Escherichia coli.
References
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