Newswise — A 1,260-mile portion of the Rio Grande flows between the United States and Mexico along the entire length of Texas' southern border, providing water for drinking, irrigation and recreational activities to communities on both sides of the border.

But according to a study in the Journal of Health and Pollution, researchers at The University of Texas at El Paso and El Paso Community College discovered that the Rio Grande is a “hotspot” for multidrug-resistant bacteria, antibiotic residues and antimicrobial resistant genes, which “may represent a public health concern” for people who use the river.

“We know there is bacteria in the Rio Grande’s water, but we wanted to see if there was antibiotic multidrug-resistant bacteria and residues because the water from the river is treated as potable drinking water and kids and their families go and swim there, especially from Mexico,” said Maria Fuentes, a student in UTEP’s Interdisciplinary Health Sciences Ph.D. Program and the paper’s first author.

“This could potentially be a public health issue because if you come into contact with the contaminated water, it could lead to more gastrointestinal infections,” she added. “It could also contribute to the problem of antibiotic resistance through the development and spreading of more genes of resistance in the environment. However, more research needs to be done to see how serious of a public health concern this is.”

Fuentes participated in the yearlong 2017 study led by Delfina C. Domínguez, Ph.D., UTEP professor of clinical laboratory science (CLS) and co-investigators Wen-Yee Lee, Ph.D., UTEP associate professor of chemistry, and Maria E. Alvarez, Ph.D., professor and coordinator of biology and chemistry programs at EPCC’s Transmountain Campus. The Edward N. and Margaret Marsh Foundation funded the study.

During the months of February, April, July, September and December, Fuentes and EPCC students sampled water and sediment from three sites within a 16-mile radius of the river from El Paso to Sunland Park, New Mexico, and Anapra, Mexico.

In addition to collecting samples, EPCC students identified the bacteria isolated from the water and sediment. UTEP’s chemistry department conducted a chemical analysis to determine which antibiotics were present in the river. Fuentes and the CLS program collaborated to identify antibiotic resistance genes found in bacteria.

The study found that antibiotics were in 92% of both water and sediment samples gathered from the Rio Grande. Genes conferring resistance were recovered from all collection sites. Of the isolated bacteria, 64% were resistant to at least two synergistic antibiotic combinations and 15% were found to be resistant to 20 or more individual antibiotics.

“This project indeed involved different expertise and resources to study a very complex and unstudied issue on antibiotics and antibiotic resistance in our region,” Lee said. “The project required researchers from biology, chemistry and health sciences to provide a better understanding of what antibiotics (are in the water) and to what extent they have impacted our region.”

Fuentes said antibiotics have found their way into the Rio Grande through animal and human waste and discharge from wastewater treatment plants, which do not have the capability to filter medications out of the water after they’ve been flushed down the toilet.

Bacteria can develop antibiotic resistance after being exposed to drugs in the water, as part of a process of natural selection which, according to the study, may lead to an increased number and severity of infections, frequency of treatment failure, allergies and alteration of intestinal flora if people come in direct contact with the water.

Despite these findings, researchers suggest more studies are needed to determine the risk of the river’s water quality to public health. In the meantime, Dominguez hopes to raise awareness about the use and misuse of antibiotics and antimicrobial resistance in the border region.

“Other studies show that antibiotic-resistant bacteria have been found in rivers all over the world, not just the Rio Grande,” Dominguez said. “But we still need to study the impact on public health. We need to conduct surveys and do testing in the community. But very minimum concentrations of antibiotics are not good at all in the river because they may impact the microflora we have.”

Alvarez said the study has not only had a profound impact on the protection of water quality and human health in the U.S.-Mexico border region, but it also enabled students from different disciplines and institutions to engage with one another.

“The collaborative nature of the projects conducted in the laboratories at UTEP and EPCC provide outstanding opportunities for students at both institutions to acquire expertise in research areas that directly affect our community,” Alvarez said. “Co-authors Stephanie Gutierrez, Daniella Sahagun and Jose Gomez were EPCC students when this project was done, and Jose Mendoza and Stephanie Bauer were former EPCC students who graduated from UTEP and NMSU.”

For Fuentes, a 2018 graduate from UTEP’s Master in Public Health program, working on the project made her more aware of how the choices people make impact the environment.

Last summer, she continued her research by looking at the water quality at water parks and irrigation sites around El Paso, after the water has been treated. This pilot study showed that genes of antibiotic-resistant bacteria have the ability to survive the filtration process and find their way back to the community. Still, more data and research are needed to understand the impact of these findings as a health concern on antibiotic resistance.

“This (Rio Grande) study has definitely made me more aware of the environment,” Fuentes said. “It makes you think about what you're drinking, what you're eating, and what you’re throwing away. This study is more a reflection of our behavior. It is about understanding how we interact with the environment and how we all have to be responsible for how we treat the environment, because we depend on it.”

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