Evaluating seasonality and pathogenicity of aeromonas in Korea using environmental DNA

Fish are sensitive to environmental perturbations, and a common signal of an unbalanced ecosystem is fish disease and death. Recently in Inje County, Korea, finding dead fish has become a common situation. Our goal was to use environmental DNA (eDNA) approaches to look for geographic and seasonal patterns in the presence of Aeromonas in waterways. First, we cultured and identified bacteria from diseased fish and screened for virulence factors. Twelve of the 21 identified bacterial species are known fish pathogens, with Aeromonas veronii and A. hydrophila being most common (37/61 total strains). Focusing on A. veronii and A. hydrophila, we used an eDNA method to screen water samples from the major waterways. We discovered geographic and seasonal patterns-Aeromonas detection was highest in Inbuk Stream and lowest during the summer.