Antibiotic-resistant bacteria are a growing public health threat, infecting at least 2 million Americans each year and killing 23,000. A University of Nebraska-Lincoln engineer's research to understand how bacteria and antibiotics interact in the environment may one day help reduce the danger.
Xu Li, assistant professor of civil engineering, recently earned a five-year, $400,000 Faculty Early Career Development Program Award from the National Science Foundation to continue his research. These prestigious awards, also known as CAREER awards, support pre-tenure faculty who exemplify the role of teacher-scholars through outstanding research, excellent education and the integration of education and research.
Hospitals have long been implicated as a major source of antibiotic-resistant bacteria, but antibiotics in the environment now also are recognized as a significant contributor. Human and livestock wastes are considered major sources of the antibiotics in the environment.
Microbes interact with antibiotics differently whether in the gastrointestinal tract, water, soils and other settings, but those interactions are not well understood, Li said. He's using an approach called quantitative proteomics to understand how antibiotics and microbes interact under different nutrient levels and types.
"The overall goal is to minimize both the microbial resistance and the antibiotics — the chemical itself — in the environment," he said.
Li and his team are using UNL's Proteomics and Metabolomics Core Facility to determine differences in protein levels within bacterial cultures exposed to different levels of nutrients and antibiotics. By correlating the resulting bacterial resistance with changes in proteins, the team can determine which proteins are involved in resistance and begin to understand their role under different nutritional conditions. 
Preliminary results suggest that bacteria starved of nutrients respond similarly to the stress of antibiotic exposure. Those bacteria already responding to nutritional stress may therefore be better able to defend against antibiotics. Understanding this relationship may lead to waste management practices or technologies to reduce bacterial resistance.
In contrast, some bacteria can break down complex environmental molecules for nourishment, and therefore may also be able to degrade complex antibiotic molecules. Identifying those bacteria and a better understanding of their capabilities could lead to harnessing bacteria to degrade antibiotic compounds, in a waste treatment facility for example. 
Decreasing antibiotic use also is critical to reducing public health and environmental threats. Li's award allows him to pursue several outreach and educational programs aimed at Nebraska livestock producers and rural students.
"Antibiotics are used extensively in the livestock industry, but a lot of the antibiotics are not absorbed by the animal, so it ends up in the waste," he said. "Without proper waste management, it's directly introduced to the environment. If we can raise awareness among livestock producers and help them develop waste management practices, maybe we can reduce the total load of antibiotics in the environment."
Li will work with UNL extension educators to give presentations and provide educational material to livestock producers. He will also develop related educational materials for rural high school students and their teachers. He said he hopes to encourage rural students to pursue environmental engineering degrees because their backgrounds could help them both develop appropriate technologies and aid in promoting new approaches in rural communities.