1. AN INVESTIGATION OF
ANTIBIOTIC RESISTANCE OF
ENVIRONMENTAL BACTERIA
IN THE MILL STREAM
By Xengie Doan with advisors Professor Sharon
Rose and Professor Melissa Marks

2. Antibiotic Resistance Spreading to
the Environment
Image credit to the
CDC

3. Antibiotic Resistance and
Environmental Bacteria
 Environmental (nonpathogenic) bacteria with
genetically based antibiotic resistances can
act as an antibacterial gene pool (Fogarty
2003).
 With intrinsic antibiotic resistances
 effluent pumps, different metabolic pathways, or
genetically inherited resistance.
 By acquiring antibiotic resistance through gene
transfer.

4. Antibiotics in our Bodies

5. Objectives
 To collect general data about the percent of
antibiotic resistance environmental bacteria in
relation to the whole population of environmental
bacteria able to be cultivated from Mill Stream
water.
 To determine whether the resistance of
environmental bacteria in the Willamette
University Mill Stream, in relation to varying
concentrations of the antibiotic Rifampicin, was
human driven or a product of natural diversity.

6. Methods
 Sample Collection from the Mill Stream
 Screening for Antibiotic Resistance in
Environmental Bacteria
 Screening for Rifampicin Resistance in
Environmental Bacteria
 Identification of Genus/Species Composition
of Rifampicin Resistant Environmental
Bacteria
http://www.pierce.ctc.edu/dept/micr
obiology/ref/images/banner.jpg

7. Results
sulfa strep rif pen nali
concentration [1] 36.42% 99.89% 13.80% 21.52% 29.80%
concentration [2] 17.11% 24.83% 17.11% 24.28% 38.07%
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
Percent
Antibiotic
% antibiotic resistance a
low and high
concentrations
0.00E+00
2.00E+02
4.00E+02
6.00E+02
8.00E+02
1.00E+03
1.20E+03
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
AverageCFU/mL
Day
Rifampicin resistance at low
and high concentrations
Antibiotic resistance of cultivated
environmental bacteria in antibiotic
infused R2A agar is found, with
rifampicin being the least effected by
antibiotics after being repeated in
triplicate.
Environmental bacteria of the
cultivated population grown at low
and high concentrations of
antibiotics in R2A agar are
Rifampicin resistant. Data was
collected from three experiments.

8. Results
4%
9%
67%
2% 3%
2%
2%
2%
2%
1% 1% 1%
3%
1%
Relative Frequency of Rifampicin Resistant Genera of
Environmental Bacteria
Alcaligenaceae
Burkholderiaceae
Comamonadaceae
Enterobacteriaceae
Flavobacteriaceae
Intrasporangiaceae
Micrococcaceae
Oxalobacteraceae
Pseudomonadaceae
Rhizobiaceae
Rhodobacteraceae
Rhodocyclaceae
Sphingomonadaceae
Streptomycetaceae
97% of identified
bacteria were of the
phylum
Proteobacteria, and
83.58% of the
environmental bacteria
belonged to the class
Betaproteobacteria.
67% of the isolated
environmental strains
are in the
Comamonadaceae
family

9. Conclusions
 Antibiotic resistance is present, but mostly
inherent
 Proteobacteria are gram negative, and
Betaproteobacteria are known to contain Class 1
integrons that are resistant to antibiotics (Gillings
2008).
 Antibiotic resistant environmental bacteria are
very diverse genetically.

10. Special Thanks and References
 Professor Sharon Rose
 Professor Melissa Marks
 Monique Bourque
 Fogarty LR, Duris JW, Aichele SS. 2003. Preliminary Survey
of Antibiotic-Resistant Fecal Indicator Bacteria and
Pathogenic Escherichia coli from River-Water Samples
Collected in Oakland County, Mich. Scientific Investigations
Report 2005-5058.
 Gillings M, Boucher Y, Labbate, Holmes A, Krishnan S, Holley
M, Stokes HW. 2008. The Evolution of Class 1 Integrons and
the Rise of Antibiotic Resistance. Journal of Bacteriology 190
(14): 5095-5100.