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Arnold School of Public Health

Sean Norman awarded CDC grant to study the risk of human exposure to environmental reservoirs of antibiotic resistant bacteria

November 30, 2018 | Erin Bluvas,

Sean Norman, associate professor of environmental health sciences and director of the Molecular Microbial Ecology Lab, has been awarded $600K from the Centers for Disease Control and Prevention. Working with a team of researchers from Ramboll Environment and Health and the Medical University of South Carolina, Norman will use the grant to study socio-ecological coupling of antibiotic resistance and the potential risk of human exposure to antibiotic resistant pathogens in bioaerosols generated during munciple wastewater treatment.

While some bacteria are naturally resistant to certain types of antibiotics, the overuse of these important drugs has led to global increases in antibiotic resistant infections, partly due to the ability of bacteria to rapidly adapt through genetic mutation and exchange of genes encoding resistance to antibiotics. Studies have often examined resistance within clinical settings; however, with increasing global population, many of the factors that select for microbial antibiotic resistance are concomitantly transferred from clinical and community settings into the environment.    

Previous research indicates that environmental compartments, such as soil, water and air, may be acting as reservoirs for antibiotic resistant bacteria. However, very little is known about the risk of transmission of resistant bacteria (or their resistance genes) from these environmental reserviors to humans.

In the present project, Norman and his team will use a case-control study design to examine the possible transfer of antibiotic resistant bacteria and genes in both wastewater treatment plants (where exposure to these bacteria is likely) and drinking water treatment plants (where exposure is far less likely). With treatment plants acting as a models of environmental reservoirs, the researchers will recruit workers at both sites, investigating the transmission of resistant bacteria from source-generated bioaerosols through an inhalation route of exposure.

“Our preliminary data have identified wastewater treatment plant bioaerosols as a potential unrecognized hazard due to the presence of high abundances of antibiotic resistant bacteria and genes, and this project will allow us to begin the next critical step of linking environmental exposure to potential human health outcomes,” explains Norman, who conducted this initial research in his laboratory with support from Ramboll Environ, Inc and the USC ASPIRE program.  

A microbiologist, Norman has 20 years of experience using various methods to describe microbial diversity within numerous ecosystems. His research focuses on how microorganisms influence ecosystem and human health and currently examines the links between climate change and microbial communities to better understand how climate alters ecosystems.

As principal investigator of the current CDC-funded project, Norman will lead the collection of human and environmental samples at six different sites during four periods to assess potential seasonal variability. The team will use high throughput DNA sequencing and bioinformatic-based approaches coupled with mathematical modeling and epidemiology to compare samples from the two types of facilities to determine whether measured differences in environmental exposures result in different risk of colonization of antibiotic resistant bacteria and genes among the microbiomes of employees.

“With this study, we hope to gain insight into possible routes of transmission of antibiotic resistant bacteria and genes from the environment to humans,” says Norman. “As antibiotic resistance is set to become one of the greatest threats to public health, it is imperative to understand the socio-ecological link and the possible routes of human exposure so that risk can be minimized.”


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