Resistência de cepas gram-negativas a antibacterianos em efluentes de hospitais públicos e na estação de tratamento de esgoto de Boa Vista-RR

Abstract

Hospital effluents may have a high load of pathogenic bacteria carrying genes encoding antibacterial resistance, such as β-lactams, the main drugs used in the empirical treatment of infections, as they have a broad spectrum of action. Resistance to these drugs has increased, being reported worldwide. Drugs, contaminated materials, biological material and patient excreta are disposed of via wastewater, turning hospital wastewater into the main source of spread of bacterial resistance in the environment. When the hospital does not pre-treat these effluents before they are released into the city's sewage network, it constitutes a vehicle through which multi-resistant bacteria can reach the sewage treatment station. As these sites are considered hotspot for the horizontal transfer of resistance genes between opportunistic pathogens and native bacteria, the possibility of reaching the receiving water body and transforming it into a reservoir is a major environmental threat. This work aimed to evaluate the sensitivity to antibacterials of Gram-negative bacteria in effluents from public hospitals and in the sewage treatment plant in the city of Boa Vista-RR, through the microbiological and molecular detection, aiming to evaluate the quality of effluents from public hospitals and compare with urban effluents. For this, effluent collections were carried out at two public hospitals in the city and at the treatment station. The samples were sown on MacConkey agar and incubated at 35ºC for 24h. After purification of the colonies, they were submitted to phenotypic identification by the biochemical series and antibiogram by the diffusion disc technique. Then, DNA was extracted for Polymerase Chain Reaction (PCR) for the genes encoding ESBL blaTEM, blaSHV and blaCTX-M. PCR and sequencing of the RNAr 16S gene were performed for the genotypic identification of species. Klebsiella pneumoniae was prevalent in hospital wastewater and in the pre-treatment of urban wastewater in the treatment plant. In post-treatment, Enterobacter cloacae was prevalent. Only in genotypic identification was it possible to identify species of the genus Aeromonas in both effluents. The antibacterial sensitivity profile revealed the presence of five ESBL strains in hospital wastewater and none in urban wastewater. However, the detection of resistance genes revealed six strains that carry at least one of the genes studied in urban effluents. In hospital effluents, eleven strains were identified as carrying at least one of the genes, including two strains (Escherichia coli and K. pneumoniae) carrying the three genes simultaneously. In one of the hospitals, 100% of the strains were found carrying resistance genes in the hospital's confluence tank, which emits directly into the city's sewage system. These results point to hospital effluents as an important source of dissemination of β-lactam resistance genes and that, despite the dilution, some strains carrying these genes reach the sewage treatment plant. Control and surveillance measures must be adopted to minimize the environmental impacts of the spread of these bacteria.