Detection of the blaCTX-M antibiotic resistance gene in freshwater streams near cattle farms in Northeast Georgia

Antibiotics are widely administered to livestock to prevent and treat infections on family-owned farms. Exposure to antibiotics can promote bacterial mutations that lead to resistance, producing antibiotic resistance genes (ARGs) that can be transferred to other bacteria. Antibiotics and ARGs are excreted in urine and feces, creating concern that agricultural runoff may introduce resistant bacteria into nearby streams.

This study investigated the presence of ARGs in water that flows through cattle farms and compared upstream and downstream locations. Water samples were collected from two family-owned farms in Northeast Georgia at three sites: upstream of the farm, within the farm boundary, and downstream. Upstream samples were taken before the stream entered the farm, while downstream samples were collected after it exited.

The study focused on the antibiotic resistance gene blaCTX-M, which encodes an enzyme that degrades β-lactam antibiotics such as penicillin. Environmental DNA (eDNA) was filtered from water samples, extracted, and analyzed using polymerase chain reaction (PCR) with a positive control to detect blaCTX-M. We hypothesize that blaCTX-M will be present in downstream samples due to livestock waste runoff but absent upstream. Detection downstream would suggest runoff as the source of ARGs, while detection at both sites would indicate additional environmental sources requiring further investigation.