Tracking antibiotic resistance gene transfers in activated sludge reactors

The dissemination of antibiotic resistances in the environment is a subject of concern because it potentially reduces our capacity to fight pathogens. Consequently to their massive use in human and veterinary medicines, antibiotics can be recovered at sub-inhibitory concentrations in the environment. Because wastewater treatment plants are the ultimate points where the charge of antibiotics can be reduced before being discharged, a research project aiming at evaluating the influence of low antibiotic concentrations on the transfer of resistance genes in activated sludge reactors has been initiated. To achieve this goal, a sensitive molecular-based approach was developed to monitor the fate of the model plasmid pB10. As little as 10 plasmid molecules remained detectable in a complex mixture containing 50 ng of DNA extracted from activated sludge, which demonstrate the sensitivity of the method and open the range of possibilities to study the influence of environmental parameters on the transfer of antibiotic resistance genes.