Environmental conditions may impact the spread of antibiotic resistance

Catastrophic events, such as flooding, may increase risk of exposure to antibiotic-resistant bacteria
December 3, 2020

Antibiotic resistance is one of the biggest public health challenges of our time, according to the Centers for Disease Control and Prevention. The spread of antibiotic resistance contributes to antibiotic-resistant infections, which are becoming more common. Each year in the United States, at least 2.8 million people get an antibiotic-resistant infection and more than 35,000 people die from this infection.

Antibiotic resistance occurs when the genes that make up characteristics of bacteria become resistant to antibiotics. These antibiotic-resistance genes are found naturally in bacteria in various environments and can be spread throughout bacterial communities. Given that antibiotic-resistance genes can be spread among different bacteria, it is important to understand conditions that may impact the ability of these antibiotic-resistance genes to spread throughout the environment.

Itza Mendoza-Sanchez, PhD, an assistant professor at the Texas A&M University School of Public Health, recently led a study that explored how a flooding event may impact the levels of antibiotic-resistance genes present in soil over time, an area of research that has yet to be addressed.

“We wanted to understand if flooding affected levels of antibiotic-resistance genes in the soil and evaluate if some of those changes were associated with changes in the soil’s microbial community,” Mendoza-Sanchez said. “It’s important because flooding may impact natural soil environments and this study may contribute to the understanding of the spread of antibiotic resistance in the environment.”

The study involved collecting soil samples from public parks in Houston affected by Hurricane Harvey at different times after the catastrophic event. DNA was extracted from the soil samples and analyzed for the presence of genes that encode for antibiotic resistance as well as changes in the soil’s microbial communities.

Results of the study indicated a diverse amount of resistance genes detected up to five months after Hurricane Harvey, with some of these antibiotic-resistance genes being attributed to changes in the microbial community. The soil samples taken 18 months post-Harvey showed a decrease in the variety of resistance genes, suggesting that risk of exposure to antibiotic-resistant bacteria via topsoil may have been higher five months compared to 18 months after the hurricane. Mendoza-Sanchez explained that future research should focus on topsoil of urban environments where high levels of antibiotic-resistance genes may increase human exposure risk.

Mendoza-Sanchez’s lab is currently working on developing tools to identify conditions that may impact levels of antibiotic-resistance, determine key factors that affect persistence and spread of antibiotic-resistance genes in the environment, and estimate potential human exposure as well as associations between exposure and antibiotic-resistant infections in humans.

“Antibiotic resistance is the perfect example of One Health,” Mendoza-Sanchez said. “Resistant bacteria may spread in and between the environment, animals and humans, and that is why this research is so important.”

-by Callie Rainosek

— Rae Lynn Mitchell

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