Dinâmica da resistência bacteriana a fármacos antimicrobianos beta-lactâmicos e vancomicina em efluentes domésticos e água de rio.

Abstract

The intensive and irrational use of antimicrobials in human, animal and agricultural health and the presence of these substances in domestic, hospital and industrial effluents, led to a scenario in which bacteria became resistant due to frequent contact with low concentrations of these antimicrobials. As a result, bacteria make use of mechanisms of resistance to these agents, and may also disseminate resistance to antimicrobials in environments. Thus, Wastewater Treatment Plant (WWTP) can be considered antimicrobial resistance gene transfer (GRA) hot-spots from antimicrobial resistant bacteria (ARB). For this purpose, this study was conducted in an WWTP and in the receiving body of the effluent located in the city of Belo Horizonte - MG. The analyzes aimed to evaluate the dynamics of bacterial resistance to antimicrobial drugs in domestic effluents. Samplings were carried out fortnightly, from August to December 2022, in which samples of Raw Effluent, UASB, Treated Effluent, water from the River upstream and from the River downstream of the effluent deposition site were collected. These samples were seeded in PCA for evaluation of THB density; in Hicrome ESBL Agar, Hicrome KPC, Hicrome MRSA, Hicrome VRE for the evaluation of ARB density; and on Cromoclin US Agar to obtain isolates belonging to the ESKAPEE group, which were tested for susceptibility to several antimicrobials recommended by BrCast. It was possible to observe that the WWTP reduced the microbial load after treatment and that the deposition of the treated effluent in the receiving body increased the density of bacteria in the downstream river in relation to the upstream river. Overall, WWTP removal of THB was 0.42 log CFU/mL and ARB was 0.48 log CFU/mL. The deposition of treated effluent in the receiving body increased the THB density by 0.66 log and 0.32 log CFU/mL of ARB in the river. Of all the isolates studied, 19.5% were part of the ESKAPEE group and showed resistance to a few antimicrobials, with only two isolates being classified as multiresistant. The results show that even reducing the organic load of pollutants, large densities of bacteria are still released into the aquatic environment, reaffirming that WWTP can contribute to the spread of resistance to antimicrobials in the ecosystem.