UCLA

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; however, this non-traditional route of antibiotic resistance acquisition has not been extensively studied. A high-throughput culture based method was developed to assess the co-selective pressure of arsenic pre-exposure to oxytetracycline resistance in planktonic cultures of Escherichia coli O55. A glucose minimal salts (GMS) media was used for the study. As2O3 and oxytetracycline hydrochloride solutions were made ranging from 1-100 ppb and 10-40 ppm, respectively. Lastly, the geochemical equilibrium model PHREEQC was used to determine the bioavailable concentrations of the metals and antibiotics in the defined GMS media. The co-selective relationship was investigated by comparing the net growth rates of the cultures pre-exposed to varying levels of arsenic to the unexposed arsenic cultures at various concentrations of oxytetracycline.