Occurrence and diversity of tetracycline resistance genes in lagoons and groundwater underlying two swine production facilities

In this study, we used PCR typing methods to assess the presence of tetracy cline resistance determinants conferring ribosomal protection in waste lago ons and in groundwater underlying two swine farms. All eight classes of gen es encoding this mechanism of resistance [tet(O), tet(Q), tet(W), tet(M), t etB(P), tet(S), tet(T), and otrA] were found in total DNA extracted from wa ter of two lagoons. These determinants were found to be seeping into the un derlying groundwater and could be detected as far as 250 m downstream from the lagoons, The identities and origin of these genes in groundwater were c onfirmed by PCR-denaturing gradient gel electrophoresis and sequence analys es. Tetracycline-resistant bacterial isolates from groundwater harbored the tet(M) gene, which was not predominant in the environmental samples and wa s identical to tet(M) from the lagoons, The presence of this gene in some t ypical soil inhabitants suggests that the vector of antibiotic resistance g ene dissemination is not limited to strains of gastrointestinal origin carr ying the gene but can be mobilized into the indigenous soil microbiota. Thi s study demonstrated that tet genes occur in the environment as a direct re sult of agriculture and suggested that groundwater may be a potential sourc e of antibiotic resistance in the food chain.