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Oxygen xml editor args.filter3/26/2023 ![]() ![]() Therefore, ARGs and ARB in treated wastewater can continue to proliferate via horizontal gene transfer (HGT) and vertical gene transfer when discharged into receiving environments.Īnalyses of sediment microbial communities near outfall sites of WWTPs have detected similar patterns of ARGs and gene classes as those in WWTP effluents ( Chu, et al., 2018). Studies on the effluent quality of conventional WWTPs have reported incomplete removal of both ARGs and ARB ( McConnell, et al., 2018, Quach-Cu, et al., 2018). With growing awareness of antibiotic resistance, numerous studies have identified WWTPs as hot spots for the propagation of ARGs and ARB ( Bouki, et al., 2013, Michael, et al., 2013). While conventional wastewater treatment plants (WWTPs) are effective at managing organics and nutrients, they are not designed or operated to treat emerging contaminants like antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB). Current projections estimate that the yearly worldwide deaths related to antibiotic resistance will reach 10 million by the year 2050 ( O’Neil, 2014). Approximately 2 million clinical cases and 23,000 deaths related to antibiotic resistant infections occur annually in the US ( Frieden, 2013). The global spread of antibiotic resistance continues to be a grave threat to human health ( Chioro, et al., 2015). Our findings suggest that exARGs located on small plasmids are preferentially taken up by cells under antibiotic pressure compared to large plasmids, which implies heterogenous HGT mechanisms among the plasmid community. ![]() This study specifically investigates the abundance of targeted iARGs and exARGs in AnMBRs in response to antibiotic pressure to quantify potential exchange of ARGs between intracellular and extracellular compartments. Further, almost no research has differentiated between iARGs and exARGs in anaerobic processes, which are being considered to replace aerobic activated sludge processes. While previous studies quantified iARGs and exARGs in wastewater treatment facilities, they did not evaluate temporal changes between the two forms. However, recent studies have detected high abundances of exARGs, implying that transformation may play a greater role in dissemination. Currently, conjugation is considered to be the dominant mechanism during wastewater treatment. Importance Antibiotic resistance dissemination is facilitated through horizontal gene transfer (HGT) of ARGs. Comparison of the iARG and exARG abundance profiles showed a potential bias for exARG uptake located on small plasmids compared to large plasmids. Quantification of targeted genes revealed an overall enrichment of intracellular ARGs (iARGs) and depletion of extracellular (exARGs) in response to antibiotics addition, which suggests exARG uptake as a significant mode of horizontal gene transfer in AnMBR effluents. ![]() ![]() This study elucidates the effect of combined antibiotics loading (ampicillin, erythromycin, and sulfamethoxazole) on the abundance of intracellular and extracellular ARGs in an AnMBR effluent over a period of five weeks. While size exclusion is effective at retaining ARB and its associated intracellular ARGs, the abundance and fate of extracellular ARGs in an AnMBR effluent have not been examined. Anaerobic membrane bioreactors (AnMBRs) are an emerging wastewater treatment technology capable of reducing the total ARGs and ARB load discharged to receiving environments compared to conventional aerobic treatment processes. The growing practice of wastewater reuse poses a significant risk to further dissemination of antibiotic resistance due to the abundance of antibiotic resistance bacteria (ARB) and antibiotic resistance genes (ARGs) in wastewater effluents. ![]()
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