Assessing variations and spatial patterns of antibiotic resistance genes and water quality in irrigation pond water

This study examined how antimicrobial-resistant bacteria spread in irrigation water, focusing on a small farm pond in Maryland. Researchers sampled 20 locations nine times over the summer of 2023 and measured two resistance genes (tetA and blaCTX-M) using digital PCR. They found large, time-dependent differences in resistance gene levels across the pond, with much higher concentrations near the banks than in the interior. These spatial patterns were stable enough to identify sampling spots that best reflected overall conditions. The elevated bank concentrations were linked to land activities and water movement, and the patterns correlated with factors such as temperature, electrical conductance, and pH. The study shows—for the first time at this fine scale in irrigation ponds—that sampling locations strongly influence AMR measurements, meaning monitoring programs must choose sampling points carefully rather than randomly.