Occurrence of antibiotics and antibiotic resistant bacteria in subtropical urban rivers in Brazil.

The occurrence of antibiotics in the natural environment has been a growing issue and correlations between this presence and developing resistance bacteria are explored. The purpose of this study was to investigate the presence of antibiotics of different classes and associated resistant bacteria, in water samples taken from urban river waters in Curitiba, Brazil. A method for the quantification of antibiotics (azithromycin, amoxicillin, norfloxacin ciprofloxacin, doxycycline and sulfamethoxazole) was developed and validated using liquid chromatography coupled with mass spectrometry. To investigate and identify coliforms resistant to these antibiotics, we performed selective microbiological culturing techniques. We detected antibiotics in our water samples; concentrations ranged from 0.13 to 4.63 μg L ^-1 , with the highest being amoxicillin at 4.63 μg L ^-1. In all water samples this study, antibiotic resistant bacteria were detected. Escherichia coli was resistant to amoxicillin, norfloxacin, ciprofloxacin, doxycycline and sulfamethoxazole. Strains producing β-lactamase with extended spectrum (ESBL and AmpC) were also found in these isolates. Enterococcus spp. displayed resistance to norfloxacin and ciprofloxacin, and some isolates were resistant to vancomycin, gentamicin and streptomycin (complementary tests). No P. aeruginosa resistant strains were observed. It is possible these antibiotics came from domestic effluents and may be contributing to the spread of bacterial resistance.
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