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 tetracycline resistance determinants conferring ribosomal protection in waste lagoons and in groundwater underlying two swine farms. All eight classes of genes encoding this mechanism of resistance [tet(O), tet(Q), tet(W), tet(M), tetB(P), tet(S), tet(T), and otrA] were found in total DNA extracted from water of two lagoons. These determinants were found to be seeping into the underlying groundwater and could be detected as far as 250 m downstream from the lagoons. The identities and origin of these genes in groundwater were confirmed by PCR-denaturing gradient gel electrophoresis and sequence analyses. Tetracycline-resistant bacterial isolates from groundwater harbored the tet(M) gene, which was not predominant in the environmental samples and was identical to tet(M) from the lagoons. The presence of this gene in some typical soil inhabitants suggests that the vector of antibiotic resistance gene dissemination is not limited to strains of gastrointestinal origin carrying the gene but can be mobilized into the indigenous soil microbiota. This study demonstrated that tet genes occur in the environment as a direct result of agriculture and suggested that groundwater may be a potential source of antibiotic resistance in the food chain

Potential environmental, ecological and health effects of soil antibiotics and ARGs

Antibiotics are biologically active compounds and are widely used in humans and animals to prevent or treat microbial diseases. Antibiotic resistance is a direct result of antibiotic use. The occurrence and dissemination of antimicrobial-resistant bacteria (ARB) and antimicrobial resistance genes (ARGs) are recognized as a major public health concern. The effect of clinically relevant ARGs and ARB that are released from anthropogenic sources, along with the excessive use of antibiotics in both human and veterinary settings, is currently considered to be a serious environmental and ecological hazard. The resistant bacteria in the environment can lead to structural changes in the microbial cell, with potential toxic effects on the balance of natural ecosystems. Soil environment is primary media, declared as recipient/reservoir and source of antimicrobial-resistant bacteria of clinical concern. The antimicrobial resistance genes interacted within these bacterial contaminants can multiply in their hosts, then transfer to other bacterial populations and be subject to further development and progression in the bacterial community. Therefore, antimicrobial-resistant bacteria that occur in the environment represent serious risks for human health