Risk Analysis of Antibiotic Resistant Genes Transferred to Raw Vegetables via Land Application of BiosolidsGrace Morgan1, Biomedical Engineering

Mentored by Dr. Kerry Hamilton2, Assistant Professor1School of Biological and Health Systems Engineering, 2School of Sustainable Engineering and the Built Environment

Question: What is the common risk of antibiotic resistance in vegetables transferred by biosolids application to crops?

BackgroundRecycled water takes various forms in agriculture due to freshwater scarcity. Wastewater reuse is a common recycling method via biosolids containing pathogen-filled waste. Antibiotic resistant gene (ARG)-carrying pathogens travel into biosolids applied to crops, contributing to the growing antibiotic resistance crisis causing 2.8M+ infections and 35,000+ deaths in the U.S. per year [1].

Project AimsDetermine the dose of ARGs transmitted by consumption of raw lettuce fertilized with biosolids for the average U.S. adult.Project phases:- Systematic review of data in current studies of ARGs in biosolids- Produce code to execute ARG dose calculations

ConclusionThe determined mean potential total daily dose of antibiotic resistant genes based on the distribution is 5.32*109 gene copies per day.Current understanding of ARGs indicates a need for determining risk of ARGs passed from wastewater environments to consumers. From the, we observe the distributed ARG dose to consumers.

Risk Analysis: Dose ModelA Python model utilized distributions of ARG concentrations in biosolids and sludge, distribution of body weight, plant biosolid uptake, EPA values on lettuce fraction consumer rate, and EPA values on average lettuce intake rate to produce a distribution of daily ARG dose. A log reduction of 1 was applied to sludge data to account for drying.

Future Work• Derivation of ARG-specific inactivation kinetic constants to integrate

into model and account for decay during produce processing time.• Assessment of exposure and risks of ARGs present in other

agricultural fertilizers such as manure. Manure is less regulated than biosolids and contains waste from animals commonly fed antibiotics.

• Development of new dose response models to progress research beyond risk and towards reduction methods and regulation.

• Investigation into other environmental factors affecting ARG fate and transport along the farm-to-fork continuum.

References and Acknowledgements[1] “Biggest Threats and Data.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 13 Mar. 2020, www.cdc.gov/drugresistance/biggest-threats.html.

Thanks to Dr. Kerry Hamilton, Ashley Heida, and Sayalee Joshi for their support on this project.

ARG dose = ARG conc.*intake rate*body weight*fraction consumers

ARG Daily Dose Ingested via Lettuce Containing Uptake of Biosolids for Average Adult in the U.S.

PRISM Flow Chart: Systematic Literature Review