Diversity of Tetracycline Resistance Genes in Bacteria Isolated from Various Agricultural Environments

A total of 350 tetracycline-resistant (Tcr) bacteria were isolated from livestock feces, farmyard manure (FYM), and soil in Japan. The isolates were classified into 28 established genera of the phyla Actinobacteria, Bacteriodetes, Firmicutes and Proteobacteria by studying partial 16S rRNA gene sequences. PCR analysis revealed that 249 of the 350 Tcr isolates contained at least 1 of 15 Tcr genes (tet genes): 140 isolates contained an efflux pump gene and 109 isolates contained a ribosomal protection protein (RPP) gene. The predominant fecal isolates were identified as members of the genera Enterococcus and Escherichia, carrying tet (M) and tet (H), respectively. The predominant soil isolates were identified as members of the genera Burkholderia and Afipia, carrying tet (Z) and tet (B), respectively. This study is the first to describe the presence of tet genes in members of the genera Bordetella, Bradyrhizobium, Burkholderia, Dyella, Flexibacter, Kurthia, Luteibacter, Lysobacter, "Nordella", Ochrobactrum, Pediococcus, Rhodopseudomonas, and Vagococcus. It has revealed that tet genes are distributed in much more diverse phylogenetic groups of bacteria in the environment than has been reported previously.