Persistence and profiles of tetracycline resistance genes in swine farms and impact of operational practices on their occurrence in farms\u27 vicinities

Animal farms are recognized as a major contributor to environmental pollution with antibiotic resistance genes, the persistence at the source and the discharge routes to the environment of which need better understanding. The presence of 16 tetracycline resistance genes (TRG) was assessed in feed, feces, manure lagoons, and the vicinities of three Georgia swine farms varied on antibiotic usage and other operational characteristics. In these farms, TRG profiles of feces and lagoons were composed of the same persistent and transient genes, with the former consistently observed in farms\u27 proximities and the latter quickly attenuated in the lagoons. Fourteen TRG incidents, 13 of which occurred in gullies, ponds, and creeks, were detected around farms. Their frequency correlated to the cumulative antibiotic usage (R2=0.99), number of lagoons (R2= 0.73), and precipitation (R2=0.83), but not to the size of herd or the amount of manure used for fertilization. Gene-specific amplicons of TRG from the farms\u27 proximities were similar to those of persistent TRG from corresponding farms. Our data suggested the independency of TRG profiles of antibiotic usage, variability in TRG persistence in manure lagoons, correlations between operational practices and TRG incidence in farms\u27 vicinities, and spills and seepage from lagoons as TRG environmental routes