Rivers and streams have been shown to play important roles in the propagation of antibiotic resistance in environmental bacteria, especially as discharge from wastewater treatment plants (WWTPs) is a major source of antibiotic resistance genes (ARGs). Being able to accurately predict the fate of ARGs in such waterways is the first step toward stemming the spread of antibiotic resistance in the environment. In addition to the transport mechanisms of the bacteria, an accurate predictive tool would also need to consider transport of the genes, which can exist both within and outside of a bacterial host cell. Current transport models do not account for natural transformation, a type of horizontal gene transfer in which extracellular ARGs (eARGs) are being taken up as free DNA by susceptible bacteria and thereby conferring resistance upon the host. Rivers affected by WWTPs are possibly susceptible to higher rates of transformation due to the elevated levels of eARG contamination found in WWTP discharge. Preliminary results from our laboratory showed that resistance among a bacterial species increases when exposed to WWTP effluent that has been filtered to remove any intracellular ARGs. These findings suggest that transformation may have a key role in rivers affected by WWTP effluent. This current study aims to identify the fate and transport of eARGs post discharge. A mathematical model that accounts for important transport mechanisms, as well as biological ones including transformation, is currently being applied to data from previous field studies to determine if such an inclusion can provide a more accurate predictive tool. Once refined, the mathematical model will then be applied to field data from the Skunk River in Ames, IA over a 54 km stretch both upstream and downstream of a WWTP using the tetW, sul1, and qnrS genes.

Fate and transport of extracellular DNA found in wastewater discharge and its role in antibiotic resistance propagation in rivers

2019 Fall National Meeting

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