Antibiotic susceptibility of E. coli strains isolated from the Rio
Grande River
V. N. León, J.A. Jackson, J. Mendoza, M. E. Alvarez
El Paso Community College, Transmountain, El Paso, Texas
Methods and Materials
The Rio Grande River is an important water resource for domestic,
agriculture, and recreational activities along the U.S.-Mexico border
region. The river has been subject to quality issues including
bacterial contamination, salinity, and low levels of dissolved oxygen
in the El Paso TX-Juarez, Mexico segment. The world-wide
emergence of antibiotic resistant gram negative bacterial strains and
the fact that the river serves as an international boundary adds a
new dimension to any efforts to monitor water quality in this area.
The Siemens MicroScan autoSCAN4 automated microbial
identification system was designed for quick identification and
antibiotic sensitivity determination of gram-negative and grampositive bacteria from clinical isolates. The objective of this study is
to test this system for the identification and antibiotic susceptibility
characterization of E. coli in river water. Water samples were
collected from the Rio Grande River from two sites previously shown
to have high numbers of E. coli: Anthony Drain (Site 1) and Anapra
Bridge (Site 2). One-liter samples were collected and 2-ml and 5-ml
aliquots were filtered using 0.45 μm filters. Filters were placed in
selective and differential media and incubated for 24hr at 37°C. E.
coli colonies were isolated and analyzed using the MicroScan
autoSCAN-4. Isolates identified with a 99.99% probability of correct
ID were selected and their antibiotic MICs determined. Five isolates
from Site 1 and seven isolates from Site 2 displayed intermediate
resistance to 11 of 25 antibiotics. In addition, two isolates from Site
1 revealed significant resistance to every antibiotic tested. The
results indicate that the MicroScan autoSCAN4 can be used to
detect antibiotic resistant strains from river water.
Step 1
Step 2
Sample collected
Gram Staining
Magenta colonies
Modified M-tec agar.
Membrane filtration was
done through a 0.45 μm
cellulose membrane filter.
MicroScan autoSCAN-4 System Report Sheet
Inoculate and scan
to confirm
E. coli isolates
getting the minimal
inhibitory
concentrations (MIC)
Isolate potential colonies
of E.coli.
Introduction
Isolate 1
μg/ml MIC (Minimial Inhibitory Conentration)
¥
Site 1 Anthony Drain
Isolate 2
Isolate 3
Isolate 4
Isolate 5
Isolate 6
Isolate 7
Isolate 8
Isolate 9
¥¥
70
¥¥
¥¥
¥¥
* Is indicative of intermediate resistance
65
60
• Five isolates from Site 1, and seven isolates from Site 2
displayed intermediate resistance to several antibiotics
including Amipicillin, Cefotaxime, Cephalotin, Norfloxacin,
Tetracycline, Tobramycin.
• Two isolates from Site 1 revealed significant resistance to
every antibiotic tested.
• The results indicate that the MicroScan autoSCAN4 can be
used to detect antibiotic resistant strains from river water.
Acknowledgements
Isolate 10
¥ Is indicative of high resistance
55
50
45
40
¥¥
¥¥
¥
¥ ¥¥
* * ¥ ¥ ¥¥
¥ ¥¥
¥
¥¥
¥¥
¥¥
¥¥
¥¥
*
* ¥¥
¥
¥ ¥¥
¥¥
¥¥
¥¥
¥¥
¥¥
¥¥
¥¥
¥
*
¥
35
30
25
20
15
10
5
0
Antibiotics
Isolate 1
Isolate 2
Isolate 3
Isolate 4
Isolate 5
Isolate 6
Isolate 7
Isolate 8
Isolate 9
Isolate 10
70
*
* Is indicative of intermediate resistance
65
60
*
*
¥ Is indicative of high resistance
55
50
45
*
40
35
30
25
20
*
* ** *
*
*
**
*
15
*
This work was supported in part by the International Boundary
Water Commission (IBWC). RISE Students and research
reported in this publication was supported in part by the National
Institute of General Medical Sciences of the National Institutes of
Health under Award Number R25GM060424. The content is
solely the responsibility of the authors and does not necessarily
represent the official views of the National Institutes of Health.
Works Cited
Site 2 Anapra Bridge
μg/ml MIC (Minimial Inhibitory Conentration)
The Rio Grande River is an important, internationally regulated
water resource for the U.S.-Mexico region where communities
interact from north of Las Cruces, NM, El Paso, TX and Ciudad
Juarez, Mexico. The Rio Grande River’s water is used as a source
of drinking water, irrigation, and for recreational purposes.
Availability of water has become a critical issue in the area and it is
a matter of great concern to the international community. The
presence of potentially pathogenic bacteria in the river is even more
concerning for this binational area. The wide use of antibiotics in
farms and in the medical field have made microorganisms resistant
to them resulting in pathogenic strains that can be multiply drug
resistant. It is very important to find ways to determine the antibiotic
sensitivity of microorganisms that cause human disease and are
found in surface water. E.coli has been used as an indicator
organism, which can give us a general picture of the extent of fecal
contamination and potentially of the presence of multiply antibiotic
resistant bacterial strains. The Siemens autoSCAN 4 microbial
identification system has the ability to ID gram positive and gram
negative bacteria with a probability of 99.99% of correct ID. It also
can give the minimal inhibitory concentrations (MIC) of some the
most widely used antibiotics in the clinical setting. The objective of
this study is to test this system for the identification and antibiotic
susceptibility characterization of E.coli in river water.
Results
*
*
* *
*
*
Bland, Christopher S., Jamie M. Ireland, Eduardo Lozano, Maria.E. Alvarez, and
Todd P. Primm, 2005. Mycobacterial Ecology of the Rio
Grande.Appl.Environ.Microbiol. 71:5719-57"Escherichia coli." Centers for Disease
Control and Prevention. Centers for Disease Control and Prevention, 22 May 2014.
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Mendoza, J. Botsford, A. Vazquez, R. Saenz, A. Valles, J. Hernandez, A. Montoya,
and M. Alvarez. 2004. Microbial Contamination and Chemical Toxicity of the Rio
Grande River. BMC Microbiology. 4:17
10
5
0
Antibiotics
Ryou, H, H. Alum, M. Alvarez, J. Mendoza, and M. Abbaszadegan. 2005. An
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