Evaluating Antibiotic Resistance Gene Correlations with Antibiotic Exposure Conditions in Anaerobic Membrane Bioreactors.

Anaerobic membrane bioreactors (AnMBRs) are an emerging technology with potential to improve energy efficiency and effluent reuse in mainstream wastewater treatment. However, their contribution to the proliferation of contaminants of emerging concern, such as antibiotic resistance genes (ARGs), remains largely unknown. The purpose of this study was to determine the effect of select influent antibiotics at varying concentrations on the presence and abundance of ARGs in an AnMBR system and its effluent. Quantification of targeted ARGs revealed distinct profiles in biomass and effluent, with genes conferring resistance to different antibiotic classes dominating in biomass (macrolides) and effluent (sulfonamides). Effluent sul1 gene abundance was strongly correlated with abundance of intl1, signifying the potential importance of mobile genetic elements in ARG release from AnMBR systems. The addition of specific antibiotics also affected normalized abundances of their related ARGs, exemplifying the potential impact of selective pressures at both low (10 μg/L) and high (250 μg/L) influent antibiotic concentrations.