Detecção de Escherichia coli resistente a antibióticos em manancial no noroeste do Rio Grande do Sul, Brasil

Abstract

Water is the most important natural resource for the balance of life on Earth and has an unquestionable importance for human health. Because of this, knowing the characteristics of the water courses used for the most diverse activities, such as irrigation, recreation, capture, treatment and subsequent destination for human consumption, among others, is exceptionally important in order to guarantee water in the necessary quality and quantity for the full enjoyment of human and animal life. However, a feature of water that has been extensively studied in recent years is the presence of antibiotic-resistant bacteria that threatens global public health. Thus, this environmental research aimed to evaluate the quali-quantitative distribution of Escherichia coli (E. coli) along the Lajeado Pardo, northwest of Rio Grande do Sul, and to analyze the susceptibility profile of bacteria to antimicrobial agents. Lajeado Pardo is covered by the drainage of five watersheds that are part of the Várzea River Basin, and its route was divided into four sampling sectors, where after collection, isolation, biochemical tests and quantification, the E. coli strains were tested for their susceptibility profile to five antibiotics. The quantitative evaluation of E. coli was performed using the most probable number (MPN) methodology in 100 mL of water, with Colilert chromogenic medium. On the other hand, the qualitative evaluation was performed using the plate isolation methodology, using different selective media Lauryl Sulfate Broth (LSB), EC and Colilert. The isolated strains were submitted to biochemical tests (catalase test and Gram stain) to aid in the identification of E. coli. In addition, the E. coli strains isolated in the four sectors were tested for their susceptibility to ampicillin, amoxicillin clavulanate, gentamicin, ciprofloxacin and chloramphenicol. It was verified that 58.2% of the water samples were above the maximum limit allowed for the classification of the water body in class 2. The sector with the most expressive samples for E. coli was sector 1, next to the water catchment dam of the Riograndense Sanitation Company (CASAN). Regarding plate isolation and biochemical tests, the presence of E. coli was found in all four sectors and media. With the isolated strains, the antibiogram was carried out, and all isolates were resistant to Ampicillin, showing marked resistance to amoxicillin, clavulanate and ciprofloxacin, with gentamicin and chloramphenicol being the antibiotics that showed greater susceptibility to the tested strains. Furthermore, the study showed that the strains isolated from environmental samples when compared to each other, by sector and through the selective isolation medium, differed statistically. Collectively, this study provided baseline data on antibiotic resistance in Lajeado Pardo in the city of Frederico Westphalen, indicating that this stock may be a reservoir of antibiotic resistance, as multiresistant antibiotic-resistant strains of E. coli were found in this location, potentially presenting a risk to public health.