Ocorrência e remoção de genes de resistência a antibióticos em sistemas simplificados de tratamento de esgoto, em Belo Horizonte

Abstract

Antimicrobial resistance has been indicated by the World Health Organization as a global problem that threatens the gains achieved with the use of antibiotics developed to date. The intense contact between bacteria, antibiotics and the possibility of horizontal gene transfer are conditions found in WWTPs that can provide increase in antimicrobial resistance. Thus, WWTPs are considered important points of bacterias resistants dissemination and ARGs and have been the subject of studies to understand how these elements spread through the environment, in order to propose ways to mitigate their spread. The removal of ARGs in sewage treatment plants has been addressed in several studies, however, knowledge about the dynamics of these elements in WWTPs is still limited, and further studies are necessary. Thus, the present study seeks to contribute to the understanding of sewage treatment plants roles in the dissemination of GRAs, quantifying the genes blaTEM (gives resistance to beta-lactams), sul1 (gives resistance to sulfonamides), tetA (gives resistance tetracillin), intI1 (integron class 1) and RNAr 16S (genetic marker of bacteria) in three simplified sewage treatment systems. The monitored systems consist of: (a) UASB reactor followed by a percolating biological filter (FBP), (b) UASB reactor followed by two high-rate algal ponds in parallel and (c) two vertical flow constructed wetlands. It was also evaluated a tertiary treatment in the system (a) with a photoreactor with emerged UV lamps, as well as the influence of the radiation dose in the removal of ARGs. The results showed concentrations of ARGs ranging from 1E + 06 to 1E + 08 in the raw sewage and from 3E + 04 to 3E + 07 in the treated effluent, considering the three treatment systems. Overall, removals of each component from the systems resulted in maximum about 1 log, however, the blaTEM gene was the most susceptible to removal (3.5 logs in UASB/LAT system), and sul1 was the most persistent. Regarding the photoreactor, no trend towards an increase in the ARGs removal was identified with an increase in the applied UV dose. The principal components analysis and Spearman showed that the COD and pH had greater influence on the concentrations of ARGs than TSS and VSS. In general, it was observed there was no increase in the concentration of ARGs after wastewater passing through the treatment systems.