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Tetracycline resistance genes in epiphytic bacteria collected from Pennsylvania stone fruit orchards.
S. BARDSLEY CAPASSO (1), K. Peter (2), H. Ngugi (3), M. Jimenez Gasco (1) (1) The Pennsylvania State University, U.S.A.; (2) The Pennsylvania State University, U.S.A.; (3) Dupont, U.S.A.
In 2012 and 2013, 648 isolates of epiphytic bacteria were collected from 8 commercial stone fruit orchards in PA. These bacteria were identified and screened for the incidence of tetracycline resistance genes, tet(A), tet(B), and tet(C). The association of management factors, including oxytetracycline use, oxytetracycline application method (e.g., alternate row middle versus complete application), and tree age, with the incidence of tetracycline resistance genes was evaluated. A total of eight bacterial genera were identified and included Pantoea (39.8%), Xanthomonas (31.9%), Pseudomonas (15.7%), Bacillus (6.3%), Curtobacterium (2.9%), Staphylococcus (2.6%), Frondihabitans (0.6%), and Rahnella (0.3%). Tetracycline resistance genes, tetA, tetB, and tetC, were found in five of the eight sampled orchards. TetB was most commonly associated with Pantoea spp. while tetC was most often found in Pseudomonas spp. The incidence of tetracycline resistance genes significantly differed among the sampled orchards. The number of oxytetracycline applications made in the year of and in the year prior to sample collection was not significantly associated with the incidence of resistance genes, tetA, tetB, and tetC; however, tree age and oxytetracycline application method were. A greater percentage of tetracycline resistance genes were recovered from old trees compared to young trees as well as from trees that had been sprayed with the alternate row middle method.