Persistence of antibiotics such as macrolides, tiamulin and salinomycin in soil.

The extensive use of veterinary drugs in agriculture leads to contamination of manure. If this manure is used as fertiliser, soil may be exposed to the respective drugs. Additionally soil exposure may stem from contaminated sewage sludge that is used on some agricultural land as fertiliser. This study focuses on the fate of antibiotics in soil. We present a 120-day degradation experiment of six commonly used antibiotics: erythromycin, roxithromycin oleandomycin, tylosin, salinomycin and tiamulin in soil as well as calculating the resulting half-lives. The half-lives were 20 days for erythromycin, 27 days for oleandomycin, 8 days for tylosin, 16 days for tiamulin and 5 days for salinomycin; all according to 1st order kinetics. The concentration of roxithromycin remained nearly unchanged during the whole experiment.