Tylosin in Hydroponic Systems: Assessing Growth and Antibiotic Residue in Lettuce Cultivation

Antibiotic persistence in the environment, including water sources, is a significant concern because of the increasing prevalence of antibiotic-resistant bacteria. Tylosin is a common macrolide antibiotic used as a growth promoter in cattle, with 71% of feedlots administering it. Antibiotics such as tylosin can persist as residual contaminants in surface water, groundwater, and wastewater. This poses a risk when these contaminated waters are used for irrigation, leading to uptake of antibiotics by plants and potentially contributing to antibiotic resistance in both humans and other organisms. To determine antibiotic uptake and its effect on crops, we conducted two experiments to test the same two concentrations of tylosin (5 and 10 mg·L –1 ) in a nutrient film technique horizontal (Expt. 1) and vertical (Expt. 2) hydroponic system by using lettuce ( Lactuca sativa ) as the model crop. A reverse-osmosis water control was used as the third treatment in each experiment. In each experiment, we measured aerial weight, head diameter, plant height, root weight, and root length after 4 weeks of exposure to the experimental treatments. Tylosin treatments reduced root weight and length significantly, by 42% and 33%, respectively, in the horizontal system. The 10 mg·L –1 tylosin treatment in the vertical system increased significantly the head diameters by 13% and the root length by 15%, compared with the other treatments. Tylosin concentrations in lettuce leaf tissue were 19 times greater than the water-only control in the horizontal experiment only. Multivariate correlation analysis revealed negative correlations between tylosin concentration and all growth parameters. These findings highlight the negative impact of tylosin bioaccumulation on hydroponically grown lettuce, raising important considerations for using recycled or alternative water sources in hydroponic agriculture, particularly in terms of food safety and crop productivity.