Evaluation of antimicrobial and heavy metal resistance profile of microrganisms isolated from Rio dos Sinos, RS, Brazil

Abstract

The Rio dos Sinos basin covers wholly or partly 32 municipalities and a land area of ​​3,600 km2. Along of its course, it receives various types of waste arising from pluvial, domestic and industrial sewage. Hence, Rio dos Sinos receives a quite diverse microbial population, allowing for the presence of microrganisms with resistance phenotype to different antibiotics and heavy metals. The main objective of this study was to evaluate the antimicrobial and heavy metals resistance profile of microrganisms isolated from crude water from sewage treatment plants which receives water from Rio dos Sinos. 410 isolated microrganisms were tested from the municipalities of Três Coroas, Esteio and Novo Hamburgo, collected once in each season of the year. The assay was performed with 13 antimicrobials. All isolates were subjected to tests of minimum inhibitory concentration (MIC) of the heavy metals chromium, copper and nickel. Also the colimetric assays and heterotrophic bacterial count were determined. Results showed a profile of 77.32% of the isolates resistant to at least one antimicrobial and 49.03% were resistant to two or more classes of antimicrobials. The antimicrobial with the highest rate of resistance was vancomycin (64.15%) and the most efficient was imipenem, with five resistant isolates. The bacteria isolated in this study shows that 44.39% were resistant to MIC above 802.27 mg/L of nickel, 40.97% were resistant to MIC above 509.24 mg/L of copper and 12.92% microorganisms were resistant to MIC above 707.04 mg/Ll of chromium. According to physico-chemical parameters, total and termotolerants coliforms, the waters of the Rio dos Sinos, up near to the source, would be classified as Class 3 standards by Conselho Nacional do Meio Ambiente-CONAMA.