Antimicrobial Resistance Genes in the Atmosphere: Emissions and Exposure

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Antibiotics are medicines used to treat bacterial diseases such as strep throat, pneumonia, and urinary tract infections. Overuse of antibiotics has led to an increase in bacteria that are resistant, meaning that the medicines are no longer effective. Antibiotic resistance is considered one of the largest public health challenges of our time. In the US, at least 2 million people become sick with antibiotic-resistant infections and 23,000 people die from them each year. The spread of antibiotic-resistant bacteria and their genes in soil and water is thought to contribute to the problem. Their presence in the atmosphere is a concern because wind can help them spread long distances. The first aim of this project is to determine how many antibiotic-resistant bacteria and their genes are present in the air in urban and rural areas. The second aim is to measure how they are released into the atmosphere from sewage treatment plants and farms. The final aim is to model how far they can travel through the air. Successful completion of this research will allow us to assess the importance of inhalation of bacteria and their genes as a transport pathway compared to contacting them through water and soil. This information can be used to develop policies and guidelines to minimize further spread of antibiotic resistance and protect public health.The spread of antimicrobial resistance genes (ARGs) in the environment is likely to play a role in transmission of resistance to humans. Most studies of ARGs in the environment have focused on water and soil, but ARGs in air are especially concerning because of their potential for long-distance transport. The overall goal of this project is to advance fundamental understanding about the sources, transport, and fate of ARGs in the atmosphere. Specific objectives are to: (1) characterize ARG concentrations and profiles in air, water, and soil samples representing background, urban, and rural settings; (2) quantify ARG emission rates to the atmosphere from wastewater treatment plants (WWTPs) and animal feeding operations; and (3) estimate the significance of inhalation exposure to ARGs. This research employs an interdisciplinary approach that leverages state-of-the-science methods in air quality engineering, microbiology, and aerosol science. Through two field studies, we will obtain measurements of ARGs and other markers of antimicrobial resistance in urban and rural areas, with a focus on WWTPs and farms. Results will include size-resolved concentrations and profiles of ARGs in air and how they relate to potential sources. We will also use data from the field studies to calculate emission rates of ARGs from WWTPs and farms via an inverse dispersion modeling approach and to assess the relative contribution of air, water, and soil to total exposure to ARGs. New knowledge about markers of antimicrobial resistance in air will be generated, including size-resolved concentrations and abundances of specific ARGs and bacteria in air; metagenomic profiles of resistomes in air, water, and soil; emission rates and emission factors for ARGs from WWTPs and animal feeding operations; and estimates of inhalation exposure to ARGs. This research will address major gaps in our understanding of antimicrobial resistance in air by producing critical new information about the prevalence of ARGs in the atmosphere, the magnitude of exposure, and their potential for long-distance transport. By advancing knowledge about ARGs in air, results will provide a more complete picture of ARGs in the environment to help reduce their spread and manage impacts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.