Abundance of six tetracycline resistance genes in wastewater lagoons at cattle feedlots with different antibiotic use strategies.

The abundance of six tetracycline resistance genes tet(O), tet(Q), tet(W), tet(M), tet(B) and tet(L), were quantified over time in wastewater lagoons at concentrated animal feeding operations (CAFO) to assess how feedlot operation affects resistance genes in downstream surface waters. Eight lagoons at five cattle feedlots in the Midwestern United States were monitored for 6 months. Resistance and 16S-rRNA gene abundances were quantified using real-time PCR, and physicochemical lagoon conditions, tetracycline levels, and other factors (e.

Quantification of tetracycline resistance genes in feedlot lagoons by real-time PCR.

A new real-time PCR method is presented that detects and quantifies three tetracycline resistance (Tcr) genes [tet(O), tet(W), and tet(Q)] in mixed microbial communities resident in feedlot lagoon wastewater. Tcr gene real-time TaqMan primer-probe sets were developed and optimized to quantify the Tcr genes present in seven different cattle feedlot lagoons, to validate the method, and to assess whether resistance gene concentrations correlate with free-tetracycline levels in lagoon waters. The method proved to be sensitive across a wide range of gene concentrations and provided consistent and reproducible results from complex lagoon water samples.