Antibiotic resistance in disinfected wastewater

What is it about?

According to the report on global surveillance of antimicrobial resistance published in 2014 by the World Health Organization (WHO), the world is heading towards a post-antibiotic era, in which common infections and minor injuries may once again kill. To successfully tackle antibiotic reistance (AR) threat not only clinical issue but also environmental one should be addressed. The release of antibiotics into the environment through treated and untreated wastewater disposal contributes to the selection and development of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). ARB and ARGs (e.g., β-lactams (blaTEM), vancomycin (vanA) and tetracycline resistance genes) have been detected both in hospital effluents and in raw and treated effluent of urban wastewater treatment plants and consequently in surface water where these effluents are disposed. Accordingly, conventional disinfection processes (e.g., chlorination and UV radiation) may be not effective in controlling the release of antibiotic resistant mobile genetic elements in aquatic environments and they can promote horizontal gene transfer. Therefore alternative/new disinfection processes should be investigated to evaluate if they can minimize the risk of AR spread. Accordingly, the aim of this work was to evaluate the effect of an advanced oxidation process (AOP) coupling UV radiation with hydrogen peroxide (H2O2) on AR transfer. In spite of the bacterial inactivation, UV/H2O2 process was not effective in the removal of the target ARGs from wastewater. On the base of the achieved results, the investigated disinfection process may not be effective in minimising AR spread into the environment. In particular, the death of bacterial cells, which results in DNA release in the treated water, may pose a risk for AR transfer to other bacteria present in the receiving water body.

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Why is it important?

This work is one of the first attempt to elucidate the effect of new water/wastewater disinfection processes on antibiotic reistance spread into the environment. A new/emerging disinfection process was investigated (UV/H2O2) and, in spite in previous works it was found to effectively inactivate different microrganisms, in this work it was found to be not effective in the reduction of antibiotic resistant genes under realistic conditions (e.g., real wastewater, typical oxidant dose).