Abstract:
Solids (sludges) from wastewater treatment are known to harbor significant
concentrations of antibiotic compounds. Wastewater sludges are commonly disposed in
landfills and by spreading onto soil. There is, therefore, an urgent need to characterize the
risks of land disposal of wastewater sludge. The reported study determines the abundance
of antibiotic resistance genes of bacteria from selected wastewater treatment plants in
central Indiana. These data are correlated to antibiotic concentrations in wastewater
sludge in order to formulate a dose-response relationship. The study has focused on two
antibiotic compounds – trimethoprim and sulfamethoxazole. Real-time PCR was used to
determine the abundance of genes among bacterial samples cultured from the sludge;
liquid chromatography-mass spectrometry was used for determination the concentrations
of antibiotic compounds present, and flame atomic absorption spectrometry was used to
measure metal concentrations. A significant relationship was found between the
concentration of cadmium (Cd) and sul1 gene abundance. Positive correlations were
observed between Cd, zinc (Zn), and lead (Pb) to dfrA1. Positive correlations were also
observed between lithium (Li) and sul1, and sulfamethoxazole and trimethoprim
concentrations and sul1 and dfrA1, respectively.
