Transcript The Effect of Ultra Violet Light Exposure On The Growth of Antibiotic

The Effect of Ultra Violet Light Exposure On The Growth of Antibiotic Resistant
Bacteria
Brad Kauffman, Department of Biology, York College
•Compare the average growth of
bacterial colonies of the different time
trials for each species of the antibiotic
resistant strains
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Enterobacter aerogenes
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Proteus mirabilis
Figure 3. Unpaired t-test comparing colony growth
between 60 and 90 seconds of exposure to UV light
Conclusions
•Any exposure to UV light causes some
bacteria mortality
•30 seconds was not enough to stop lawn
growth although it seemed to revert some
of the mutants back to sensitive strains
without fully killing everything
•The results of the unpaired t-tests show
that there are significant differences in the
number of bacteria able to grow with
exposure to 60 and 90 seconds of UV light
exposure
1. Fitzwater, J. 1961. Bacteriological Effect of Ultraviolet Light on a
Surgical Instrument Table. The American Journal of Nursing 61:71-75.
2. Meckes, Mark C. 1981. Effect of UV Light Disinfection on AntibioticResistant
Coliforms in Wastewater Effluents. Applied and Environmental
Microbiology. 43:371-377
3. Muhammed, Amir, and Setlow, Jane K. 1969. Ultraviolet-Induced
Decrease in Integration of Haemophilus influenzae Transforming
Deoxyribonucleic Acid in Sensitive and Resistant Cells. American Society
for Microbiology 104:44-48
4. Vermeulen, N., Keeler, Werden J., Nandakumar K., and Leung, K.T.
2007. The Bactericidal Effect of Ultraviolet and Visible Light on
Escherichia coli. Biotechnology and Bioengineering.
5. Washington, M. Todd, Johnson, Robert E., Prakash, Louise, Prakish,
Satya. 2000. Accuracy of thymine–thymine dimer bypass by
Saccharomyces cerevisiae DNA polymerase η. Proceedings of the
National Academy of Sciences. 97:3094-3099
6. Waites, W.M., Harding, S.E., Fowler, D.R., Jones, S.H., Shaw, D., and
Martin, M. 1988. The destruction of spores of Bacillus subtilis by the
combined effects of hydrogen peroxide and ultraviolet light. Letters in
Applied Microbiology. 7:139-140
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Compared data of each species’ 60
and 90 second growth results to exposure to UV light.
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Literature Cited
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Comparison of 60 vs 90 seconds exposure to UV light
Followed same procedure for 60 and 90
seconds for each species. Performing
10 trials for each of the remaining species.
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•The extra 30 seconds of exposure from 60
to 90 seconds made a big difference in
bactericidal activity
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Figure 1. Unpaired t-test comparing colony growth
between 60 and 90 seconds of exposure to UV light
•Isolate antibiotic and sensitive strains
of different species of bacteria
•Expose antibiotic resistant bacteria to
different time intervals of ultraviolet
light, consisting of 30, 60, and 90
seconds
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Objectives
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•UV light is becoming very popular as a step in
sterilizing or sanitizing certain things such as
surgical instrument tables, incoming air from
vents leading into operating rooms and
wastewater in sewage treatment plants (Fitzwater
1961) and (Meckes 1981).
Also put sensitive strains
on agar plates along
with antibiotic discs
without subjecting to UV
light. These were used
as controls to make sure
my mutants were still
resistant at each trial.
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•UV is light also effective at destroying bacteria
that are antibiotic resistant as well as bacteria
that can lay dormant by forming spores (Waites et
al. 1988).
Comparison of 60 vs 90 seconds exposure to UV light
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•Lower wavelengths in the UV spectrum have
enough energy to disrupt these bonds making
them unstable which can cause the dimers which
eventually leads to the bactericidal effects
Placed each mutant species in UV
light hood for 30 seconds 10
different times. Placed
antibiotic discs on agar after
exposure on mutant strains.
•Comparison of 60 and 90
second time within same
species using un-paired t-test
showed the means of colony
growth to be significantly
different
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•Certain wavelengths of energy are responsible
for disrupting certain bonds such as the P-O, OH, and N-H bonds which are important in the
structure of DNA (Vermeulen et al. 2007).
Took samples of each mutant and
resistant species and spread on
separate nutrient agar plate.
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•Bacteria have repair mechanisms but sometimes
too many excisions are made and after too much
exposure bacterial repair mechanisms cannot
keep up with damage and the DNA becomes
denatured and destroyed (Muhammed 1969).
•UV light exposure for 60 and
90 seconds had good
bactericidal activity.
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•UV light is absorbed by double bonds in
pyrimidine bases and the energy released from
bond breakage is used to form pyrimidine dimers
(Washington et al. 2000).
Number of colonies that grew
•Ultraviolet light can be an effective bactericidal
agent, due to its interference in DNA synthesis
and repair
•Bacterial growth was found on
most 30 second time trials,
although some seemed to
revert back to sensitive
because zones of inhibition
were present.
Re-tested mutant strains for
resistance to other antibiotics.
Also isolated sensitive strains of
the same species for use as controls
Number of colonies that grew
Introduction
•Initial isolations found bacteria
to be multi-resistant to
chloramphenicol, erythromycin,
and ampicillin.
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Isolated pure colonies of mutant
bacteria resistant to one antibiotic
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Results
Methods
Number of colonies that grew
Comparison of 60 vs 90 seconds exposure to UV light
Serratia marcesens
Figure 2. Unpaired t-test comparing colony growth
between 60 and 90 seconds of exposure to UV light
Acknowledgements
I would like to thank Dr. Mathur for all her help in the
idea and design of the experiment as well as her help
throughout the entire process.