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(73-08) Summary of effects of antibiotics on environmental bacteria with a simple risk assessment. Alexy, Radka*,1, Kümpel, Tina1, Kümmerer, Klaus1, 1 Institute of Environmental Medicine and Hospital Epidemiology, University Hospital Freiburg, Hugstetter Strasse 55, Freiburg, Germany ABSTRACT- After application antibiotics are mainly excreted unchanged and therefore emitted into waste water. The main part of sewage treatment is biodegradation of the substances present in waste water. Therefore the determination of their biodegradability as well as the toxic effects on bacteria and water-dwelling organisms is of great importance. There is little information available on the occurrence, fate and effects of antibiotics in the environment (Halling-Sorensen et al. 1998, Kuemmerer 2001a,b). For this reason 18 antibiotics were selected for testing of biodegradability and toxic effects. The results of some tests (for example respiratory inhibition test, nitrification inhibition test) indicated the necessity of a modification of the test conditions in relation to the specific mode of action of the substances under investigation. Testing the influence of antibiotics on the bacterial growth was performed not only with the gram- bacterium Pseudomonas putida (as described in the standard procedure), but also with the newly developed test using gram+ bacteria Enterococcus faecalis. The Closed Bottle Test (a test for determining the ready biodegradability) was performed according to standard procedure. In addition HPLC-analysis was done in order to detect primary elimination. The results of the tests were used for a simple risk assessment with PEC/PNEC-ration as a first step of risk management. This investigations were provided within the scope of Project, that is supplied by the Federal Environmental Agency in Berlin (Grand No.: 298 637 22). Key words: antibiotic, environmental bacteria, risk assessment |
