Impact of Wastewater Effluent on Antibiotic Resistant Phenotypes
Exposure to wastewater treatment effluent could result in an increase in antibiotic resistance phenotypes in bacteria; potentially fueling river systems with antibiotic resistant pathogenic bacteria that will spread downstream to recreational water bodies and public water sources. The goal of this team-based research project is to investigate the extent to which wastewater effluent impacts antibiotic resistance and whether there are specific conditions that exacerbate this issue. Six undergraduate students are running Minimum Inhibitory Concentration (MIC) experiments to discover if the wastewater from the Ames Water Pollution Control Facility contributes to phenotypic antibiotic resistance depending on the type of bacteria, antibiotic, and wastewater effluent disinfection method. For the MIC experiment, the water and bacteria concentrations are held constant, while the concentration of antibiotic is adjusted by serial dilution. The MIC value is the lowest concentration of antibiotic that results in inhibition of bacterial growth; if wastewater effluent increases antibiotic resistance, the MIC of samples with wastewater effluent would be greater than the MIC of the control samples. Untreated, chlorinated, and heat-inactivated wastewater effluents are compared to the control (receiving nanopure water) in each experiment. The compiled information will explain if wastewater effluent contributes to phenotypic antibiotic resistance to tetracycline, kanamycin, ciprofloxacin, sulfamethoxazol, and erythromycin in three model bacterial strains, Escherichia coli, Bacillus cereus, and Serratia marcescens. Preliminary data thus far suggest that wastewater effluent can increase antibiotic resistance in the bacterial strains tested. The bigger picture impact of the results from this study will also be discussed.