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. 2019 Aug 22;9(23):190912.
doi: 10.5696/2156-9614-9.23.190912. eCollection 2019 Sep.

Assessment of Antibiotic Levels, Multi-Drug Resistant Bacteria and Genetic Biomarkers in the Waters of the Rio Grande River Between the United States-Mexico Border

Maria D Fuentes  1 , Stephanie Gutierrez  2 , Daniella Sahagun  2 , Jose Gomez  2 , Jose Mendoza  2 , Cameron C Ellis  3 , Stephanie Bauer  3 , Jonathan Blattner  3 , Wen-Yee Lee  3 , Maria Alvarez  2 , Delfina C Domínguez  4
Affiliations

Assessment of Antibiotic Levels, Multi-Drug Resistant Bacteria and Genetic Biomarkers in the Waters of the Rio Grande River Between the United States-Mexico Border

Maria D Fuentes et al. J Health Pollut. .

Abstract

Background: The worldwide emergence of multi-drug resistant bacteria has become a health crisis, as fewer or sometimes no antimicrobial agents are effective against these bacteria. The Rio Grande River is the natural boundary between the United States (US) and Mexico. It spans a border region between Texas, New Mexico and Mexico. Underserved populations on the Mexican side use the river for recreational purposes, while on the US side, the river is used for irrigation and as a source of drinking water.

Objectives: The purpose of the present study was to evaluate the concentration of antibiotic residues, to determine the presence of genetic elements conferring antibiotic resistance and to characterize multi-drug resistant bacteria in the waters of the Rio Grande River.

Methods: Water samples were obtained from the Rio Grande River. Deoxyribonucleic acid (DNA) was extracted from both isolated bacteria and directly from the water. Amplification of selected genetic elements was accomplished by polymerase chain reaction. Identification and isolation of bacteria was performed through MicroScan autoSCAN-4. Fecal contamination was assessed by IDEXX Colilert. Antibiotic residues were determined by liquid chromatography and mass spectrometry.

Results: Antibiotics were found in 92% of both water and sediment samples. Antibiotic concentrations ranged from 0.38 ng/L - 742.73 ng/L and 0.39 ng/l - 66.3 ng/g dry weight in water and sediment samples, respectively. Genetic elements conferring resistance were recovered from all collection sites. Of the isolated bacteria, 91 (64.08%) were resistant to at least two synergistic antibiotic combinations and 11 (14.79%) were found to be resistant to 20 or more individual antibiotics. Fecal contamination was higher during the months of April and July.

Conclusions: The 26 km segment of the Rio Grande River from Sunland Park NM to El Paso, TX and Juarez, Mexico is an area of concern due to poor water quality. The presence of multidrug resistant bacteria, antibiotics and mobile genetic elements may be a health hazard for the surrounding populations of this binational border region. Policies need to be developed for the appropriate management of the environmental natural resources in this border region.

Competing interests: The authors declare no competing financial interests.

Keywords: Rio Grande River; antibiotics; antimicrobial resistance; extended-spectrum beta-lactamase (ESBL); horizontal gene transfer; integrons; mobile genetic elements.

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Figures

Figure 1
Figure 1
Rio Grande sampling sites: Site 1: Sunland Park area near waste water treatment plant (NM); Site 2: Riverbend/Courchesne area near waste water treatment plant effluent (Texas); Site 3: Anapra area (Juarez, Mexico and Texas)
Figure 2
Figure 2
Most probable number (MPN) values of E coli (per 100 ml) identified from water samples collected from the Rio Grande River. Site 1: Sunland park area near waste water treatment plant (NM); Site 2: Riverbend/Courchesne area (Texas); Site 3: Anapra area (Juarez, Mexico and Texas). Water fecal contamination was determined by the IDEXX Colilert MPN method.
Figure 3
Figure 3
Percentage of ESBL genes (TEM, SHV and CTX-M) identified from water samples (N= 15) from the Rio Grande River. Amplification of selected extended spectrum beta-lactamase (ESBL) genes was accomplished by PCR as described in methods section.
Figure 4
Figure 4
Percentage of Class 1 and Class 2 integrons identified from water samples (N=15) from the Rio Grande River. Amplification of selected Class 1 and 2 integrons was accomplished by PCR as described in the Methods section.
Figure 5
Figure 5
Average concentrations (ng/L) of antimicrobial residues identified from water samples (N= 15) from the Rio Grande River. Antibiotic residues were determined by liquid chromatography and mass spectrometry.
Figure 6
Figure 6
Average concentrations of antimicrobial residues (ng/g) identified from sediment samples (N= 15) from the Rio Grande River. Antibiotic residues were determined by liquid chromatography and mass spectrometry.
See this image and copyright information in PMC

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