Elimination and Redistribution of Intracellular and Extracellular Antibiotic Resistance Genes in Water and Wastewater Disinfection Processes: A Review

Abstract

Antibiotic resistance genes (ARGs) have been identified as emerging contaminants in water and wastewater. Concerns have been raised of whether disinfection processes can effectively eliminate ARGs and thus mitigate their spread. Due to the different existing forms and dissemination pathways, intracellular ARGs (iARGs) and extracellular ARGs (eARGs) have different responses to disinfection processes. This review compares the elimination of iARGs and eARGs in representative disinfection processes applied at water and wastewater treatment plants, including treatment by chlorine, chloramine, chlorine dioxide, ozone, ultraviolet irradiation (UV), and combination of UV with chemicals. Meanwhile, the redistribution of ARGs upon disinfection processes is highlighted. Elimination efficiencies of ARGs generally follow the order: ozone > chlorine ≫ chlorine dioxide > chloramine. The elimination of naked eARGs could be up to 4-log higher than that of iARGs. Notably, these disinfectants and the resulting disinfection byproducts formed in disinfection process can select antibiotic resistant bacteria (ARB) and increase relative abundances of iARGs. Under practical disinfectant exposure, elevated abundances of eARGs may be observed. Low doses of chlorine and chloramine tend to enhance the transfer of ARGs from intracellular to extracellular forms. To selectively control ARGs and associated risks and meanwhile minimize the unintended consequences, the disinfection practice may warrant optimization.

Non-Canonical Aspects of Antibiotics and Antibiotic Resistance

“…While WWTPs can significantly reduce the amount of antibiotics released into the environment [ 47 ], they act as a sort of reactor for the shuffling and concentration of AR genes and bacteria (e.g., Ref. [ 300 ]), and although some treatment processes can efficiently remove AR [ 301 ], they are seldom used, especially in poor countries, whileothers can actually select for AR [ 302 ]. By putting together pathogens, commensals and environmental bacteria, AR and mobility genes, and selective pressures favoring AR, WW is an ideal environment for the emergence of mobile AR genes that can then be spread into different bacteria, including pathogens [ 303 , 304 ].…”

A Critical Review of AMR Risks Arising as a Consequence of Using Biocides and Certain Metals in Food Animal Production

“…Soil and water harbor large environmental reservoirs of a rich microbiota where released genes may integrate into new bacterial genomes through HGT [70,71]. This phenomenon is well-documented in wastewater and drinking water treatment [72] but our literature search did not identify any specific studies that have investigated this in a food animal production context.…”