Transport and persistence of tylosin-resistant enterococci, genes, and tylosin in soil and drainage water from fields receiving Swine manure.

Land application of manure from tylosin-treated swine introduces tylosin, tylosin-resistant enterococci, and erythromycin resistant rRNA methylase () genes, which confer resistance to tylosin. This study documents the persistence and transport of tylosin-resistant enterococci, genes, and tylosin in tile-drained chisel plow and no-till agricultural fields treated with liquid swine manure in alternating years. Between 70 and 100% of the enterococci in manure were resistant to tylosin and B concentrations exceeded 10 copies g manure, while the mean F concentrations exceeded 10 copies g manure (T was not detected). The mean concentration of tylosin was 73 ng g manure. Soil collected from the manure injection band closely following application contained >10 copies g soil of both B and F in 2010 and >10 copies g soil after the 2011 application compared to 3 × 10 to 3 × 10 copies g soil in the no-manure control plots. Gene abundances declined over the subsequent 2-yr period to levels similar to those in the no-manure controls. Concentrations of enterococci in tile water were low, while tylosin-resistant enterococci were rarely detected. In approximately 75% of tile water samples, B was detected, and F was detected in 30% of tile water samples, but levels of these genes were not elevated due to manure application, and no difference was found between tillage practices. These results show that tylosin usage increased the short-term occurrence of tylosin-resistant enterococci, genes, and tylosin in soils but had minimal effect on tile drainage water quality in years of average to below average precipitation.