Fluoroquinolone antibiotics in a hospital sewage line; occurrence, distribution and impact on bacterial resistance

In hospital sewage lines, human faecal bacteria are exposed to antibiotics, posing a risk for selection of antibiotic resistant microorganisms. We constructed a system for continuous sampling in a hospital sewage line that allowed us to study longitudinal establishment of bacteria, concentrations of antibiotics, and selection of bacterial resistance in waste water, sediment and biofilm. The focus in this study was on fluoroquinolones, a widely used group of antibiotics with increasing resistance problems. We found low levels of ciprofloxacin and ofloxacin in waste water but high concentrations in sediment. Despite the high levels of fluoroquinolones bound to sediment, we did not find any development of resistance against fluoroquinolones in Enterobacteriacae spp. and faecal enterococci isolated from sediment.