Framework for establishing regulatory guidelines to control antibiotic resistance in treated effluents

Abstract Antibiotic resistance is a major threat to human-health and wellbeing. Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are environmental contaminants that circulate among humans, animals and the environment. In urban areas, wastewater treatment plants are the major recipients of these contaminants. Despite the partial elimination during treatment, final effluents, even after disinfection, contain high doses of ARB&ARG. The consequent continuous discharge of these effluents has important adverse impacts, which are particularly intense in vulnerable and deteriorated receiving environments (e.g., due to pollution, droughts or floods, reduced biodiversity). ARB&ARGs are biological contaminants capable of self-replication and horizontal gene-transfer, capabilities that due to pollution-induced selective pressure effects or absence of competition can be enhanced in deteriorated environments. Moreover, as other contaminants, ARB&ARGs can be transported, mainly through water, increasing the risks of circling back as a source of exposure to humans. The current knowledge about antibiotic resistance implications in terms of environmental contamination and risks to human-health, as well as the advances on wastewater treatment technology and antibiotic resistance quantification methods, support the need and timeliness of implementing regular wastewater monitoring systems. Because no single chemical or microbiological parameter can be used to infer the antibiotic resistance load, its specific monitoring should be part of the parameters used to assess wastewater quality. The definition of minimal requirements and integrated monitoring are essential to map antibiotic resistance at time- and space scales, and to design and implement corrective measures. These goals are technically and economically feasible and should be incorporated into wastewater quality directives. Graphical abstract