When sulfadiazine enters the environment via manure, it does not appear to persist for long
German researchers have obtained further funding for their project examining the effects of veterinary antibiotics on the environment. 
Photo: Jean Scheijen
Several thousand tonnes of these drugs are administered to European livestock each year. Up to 90% of these are excreted unchanged, and end up in the soil. Since 2005, scientists from several German research institutes have been studying the effects of sulfadiazine and difloxacin in the environment. The project is now set to continue for a further three years, after gaining funding from the German Research Foundation, DFG.
While the study has revealed that the drugs do not appear to contaminate groundwater, the researchers have nonetheless observed an increase in resistant bacteria in soil treated with manure that contained the antibiotics.
However, this does not mean that the drugs are no longer present, say the researchers. "A small amount apparently becomes trapped in microscopic pores in the soil, where it can presumably persist for many years," said Dr Wulf Amelung, a soil scientist at Bonn University. The drugs do not appear to be biologically active in this form, but the researchers now hope to find whether they can be released and reactivated under certain conditions.
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