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Implications of the presence of antibiotic resistant genes in wastewater

  • October 29th, 2020
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On October 29, the DAM Chair held a Webinar on the possible effects that may arise from the presence of antibiotic resistant genes (ARG) in wastewater.

Participating in the Webinar were Dr. Moustapha Harb, Assistant Professor of Civil and Environmental Engineering at the American University of Lebanon (LAU), and Dr. Maite Muniesa, Professor of the Department of Genetics, Microbiology and Statistics at the University of Barcelona. The webinar congregated 55 attendees of different ambits (administration, eduation and company).

Dr. Harb's presentation entitled “Interpreting the implications of observed antibiotic resistance gene data in various water reuse scenarios”. In his talk, Dr. Harb highlighted that both antibiotics and other emerging pollutants affect the increased presence of ARG in wastewater. All these contaminants clearly modify the microbial composition in the environment, so more research is needed in relation to the effects of current treatments due to the interaction between the microbial composition and the resistance genes. Moreover, the wastewater treatment technologies applied in each case, as well as their operating parameters, play an important role in the generation and dynamics of ARGs. Dr. Harb stressed the importance of the application of advanced tertiary treatments in the treatment of wastewater to reduce the dissemination of antibiotic-resistant genes in the receiving environments of treated water and promote the reuse of these waters.

In the presentation by Dr. Muniesa, entitled "Presence, prevalence and new mobility vehicles of antibiotic resistance genes in wastewater", it was revealed that the abusive use of antibiotics in humans and animals has exerted selective pressure on the bacterial communities present in the receiving environments of the contaminated waters, thus favouring the appearance of resistance mechanisms. Likewise, Dr. Muniesa highlighted the key role that bacteriophages play in ARG transfer, given their greater prevalence in different environmental conditions. Therefore, studies should not only focus on the analysis of ARG-bearing bacteria but also on the analysis of ARG-bearing phage. The ARGs that are packed inside the sludge have a higher resistance and, therefore, their ability to transfer will increase, making it possible for them to reach the crops if the sludge is applied as an organic amendment. In this regard, Dr. Muniesa indicated that neither the mesophilic digestion processes nor the composting processes allow a total ARG removal, since in these processes the elimination of certain organisms occurs, but the appearance of others is favoured, so there could still be an ARG transfer. Even in thermophilic treatments, the presence of bacteriophages is observed, according to Dr. Muniesa.

Both speakers highlighted that both the treated wastewater and the sludge generated in its treatment are vectors of ARG transference to the natural environment. To mitigate the potential impacts associated with the presence of ARG, action must be taken in two directions: on the one hand, the contribution of antibiotics to wastewater must be reduced, or at least in certain types of antibiotics such as quinolones, with greater capacity generation of ARG; on the other, adequate treatments should be considered both in water and in sludge to comply with future legislation that includes, after an adequate risk analysis, the ARG as new emerging pollutants.