With increased antibiotics usage over recent decades, there has been an emerging concern about the accelerated development of antibiotics resistance in the environment. This development poses several public health concerns, such as, the higher frequency of multiple drug resistant bacteria both in the environment and in clinical settings. Exposure to metals can increase antibiotic resistance through co-selective pressure, a poorly studied, non-traditional route of antibiotic resistance acquisition (Baker-Austin et al. 2006). Generally, toxic metals concentrations and speciation vary spatially in soil and are influenced by environmental conditions, along with anthropogenic influences. Currently, a major source of antibiotics into soil is the practice of land application of manure and biosolids onto agricultural land (Farhrenfeld et al., 2014). In California, the Central Valley is a highly agricultural region with high incidence of elevated metals contamination. The aim of this study was to evaluate the effect of toxic metals on oxytetracycline resistance in Escherichia coli DH5a (E. coli DH5a) in amended and non-amended, unsaturated soil columns. Soil, manure, and bio-solids samples were collected from the Central Valley and characterized for critical physicochemical properties to be used in geochemical modeling using PHREEQC, the USGS software for equilibrium and kinetic modeling, as well as 1-D transport. Metals, oxytetracycline, E. coli DH5a, and free DNA adsorption isotherms were also determined in soil, manure, and biosolids, parameters used for PHREEQC, as well. Ultimately, differential survivability conferred by co-selective pressure was determined by optical density measurement at 600 nm to determine growth rate, along with qPCR measurement of tet gene maintenance.

Toxic metals exert co-selective pressure for oxytetracycline resistance in unsaturated, manure and biosolids amended soil columns

248th National Meeting (2014)

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