Transport of Tylosin and Tylosin-Resistance Genes In Subsurface Drainage Water From Manured Fields.

Animal agriculture appears to contribute to the spread of antibiotic resistance genes, but few studies have quantified gene transport in agricultural fields. The transport of tylosin, tylosin-resistance genes (erm B, F, A) and tylosin-resistant Enterococcus were measured in tile drainage water from plots treated with manure from tylosin-treated swine.  Enterococcus measured after fall manure application reached 700 cells/g soil, but tylosin-resistant Enterococcus accounted for less than 10% of the total soil population.  Enterococcus soil populations declined over the winter.  Tylosin-resistant bacteria were detected in tile drainage water only in the early spring and tylosin was sporadically detected in drainage water at concentrations below 1 ng/L. The abundance of erm genes was measured by qPCR and those results will be discussed.