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Antibiotic susceptibility of E. coli strains isolated from the Rio
Grande River
C. E. Okpala, 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
resistance 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
gram-positive 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 (1) and Anapra Bridge (2). One-liter
samples were collected and 2-ml and 5-ml aliquots were
filtered using 0.45mm 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.
Two isolates from Site 1 and seven isolates from Site 2
displayed intermediate resistance to several antibiotics
including Amipicillin, Cefotaxime, Cephalotin, Norfloxacin,
Tetracycline, Tobramycin. 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 0.47 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
objective of this study is to test this system for the
identification and antibiotic susceptibility characterization of
E.coli in river water.
MIC (Minimial Inhibitory Conentration (mg/ml)
Site 1 Anthony Drain
Isolate 1
Isolate 2
35
Isolate 3
Isolate 4
Isolate 5
Isolate 6
Isolate 7
Isolate 8
Isolate 9
*
* Is indicative of intermediate
resistance
30
25
20
*
*
*
*
*
*
*
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.
*
15
*
10
*
5
0
Works Cited
Site 2 Anapra Bridge
Isolate 1
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Isolate 2
Isolate 3
Isolate 4
Isolate 5
Isolate 6
11 isolates from Site 1 and 17 isolates from Site 2
displayed intermediate resistance to several antibiotics
including Amipicillin, Cefotaxime, Cephalotin, Norfloxacin,
Tetracycline, Tobramycin. The results indicate that the
MicroScan autoSCAN4 can be used to detect antibiotic
resistant strains from river water.
Acknowledgements
Isolate 10
Antibiotics
MIC (Minimial Inhibitory Conentration (mg/ml)
The Rio Grande River is a very vital source of drinking
water and irrigation, as well as for recreation along the
region of El Paso, in the border of Texas and Juarez. It
can also serve as a reservoir for many microorganisms
from municipal streams as well as illegal dumping. The
wide use of antibiotics in farms and in the medical field
have made microorganisms resistant to them resulting in
pathogenic strains that can cause disease in humans. It
is very important to find ways to determine the sensibility
to antibiotic of microorganisms related to human beings
in the surface water. E.coli found in the gut of many warm
blooded animals including humans. Finding the sensitivity
to antibiotics of E.coli can give us a general pictures of
the resistance to antibiotics developing in the river. The
Seimens 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 use antibiotics in the clinical setting. The
Results
Isolate 7
Isolate 8
Isolate 9
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
Isolate 10
* *
*
* Is indicative of intermediate
resistance
"Escherichia coli." Centers for Disease Control and Prevention. Centers for
Disease Control and Prevention, 22 May 2014. Web. 24 July 2014.
*
****
*
*
**
*
*
Antibiotics
*
*
*
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
Ryou, H, H. Alum, M. Alvarez, J. Mendoza, and M. Abbaszadegan. 2005. An
assessment of Water Quality and Microbial Risk in Rio Grande Basin in the
United States- Mexican Border Region. Journal of Water and Health 3.2:209218
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