Oct 10, 2019

Antibiotic-Resistant Genes Prevalent in California’s Groundwater Samples

The spread of antibiotic-resistant genes (ARGs) through the water system could put public safety at risk. 

Antibiotic-resistant genes in water

New safety concerns emerge after researchers in Southern Calif. discovered the prevalence of antibiotic resistant genes (ARG) in groundwater samples. This raises concerns over the spread of ARGs through the water system and an increase in development of antibiotic-resistant superbugs.

Researchers studied and compared samples from an advanced groundwater treatment facility in Southern California and groundwater aquifers to detect differences in ARG concentrations, according to Science Daily. They found that the advanced groundwater treatment facility reduced nearly all targeted ARGs to below detection limits, but groundwater samples had a pervading presence of ARGs in both control locations recharged with water from the advanced water treatment facility. 

This research is a response to the increasing water shortages and droughts brought on by climate change. As policymakers look into wastewater recycling as a sustainable way to fill the gap in water resources, new and emerging contaminants, such as ARGs, pose a risk to water systems and public health, according to the study.  

"ARGs are not regulated in any way and are a challenging emerging contaminant of concern due to our reliance on biological treatment in the engineered water cycle," said Adam Smith, assistant professor in the Sonny Astani Department of Civil and Environmental Engineering at the University of Southern California. "Because they are biological contaminants—small fragments of DNA that are released to the environment—bacteria present in receiving environments can uptake them, becoming resistant themselves and further perpetuating the spread of resistance."

ARGs and antibiotic-resistant pathogens are on the rise in water sources as a result of the overuse of antibiotics in general, according to the Centers for Disease Control and Prevention Control and Prevention. 

Wastewater treatment plants are not generally designed to remove micropollutants, such as antibiotics, so they usually persist in treatment systems, leading to high densities of ARG resistant bacteria at different stages of treatment, reported the study. When this water is introduced into an aquifer, where ARGs already naturally occur, it can become contaminated with ARGs and antibiotic-resistant bacteria. 

Wastewater reuse is a preferable course of action to manage the global water supply, as opposed to options such as desalination, which is expensive and energy inefficient by comparison. Nevertheless, with this method comes the possibility of spreading antibiotic-resistance.

"Lessening the global spread of antibiotic-resistance will require an interdisciplinary approach that spans environmental and clinical systems. We must act fast before we enter a so called 'post-antibiotic world' where bacterial infections become impossible to treat," Smith said.

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