Determining the contribution of stream morphometry and microbial extracellular polymeric substances in the spread...

Bacteria that have antimicrobial resistance (AMR) are emerging global bio-pollutants owing to their dissemination through food, animals, and the environment. However, few studies have combined the internal factors related to bacterial physiology with external factors-specifically morphometric river analysis-to demonstrate the effects on the spread of AMR. Extracellular polymeric substances (EPS) within the biofilm matrix form unique micro-ecosystems that can influence the physiology and genetics of resistant bacteria and their associated genes. We investigated whether AMR dissemination associated with EPS production is significantly related to meteorological factors, stream morphology, and land use and land cover. By using a geographic information system, we explored resistant Escherichia coli bacteria and genes in diverse riverine habitats, water columns, sediment beds, and rock surfaces of the Yasu River, the largest stream flowing into Lake Biwa, Japan's largest freshwater lake. EPS production in sediment and rock beds resulted in a significant increase in the abundance of resistant bacteria and genes. However, this was quickly altered by precipitation and stream flow dynamics. Land use had a greater impact than stream length or stream density, providing a better understanding of how AMR is disseminated in the environment.