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(85-08) Effects of antibiotics used in animal production on soil microbial communities. Schmitt, Heike*,1, Tolls, Johannes1, van Beelen, Patrick2, van Leeuwen, Kees2, 1 University of Utrecht, Utrecht, NL -2 RIVM, Bilthoven, NL - ABSTRACT- Veterinary drugs used in animal production can enter the environment through manuring of agricultural soils with slurry of treated animals. The environmental hazards associated with this exposure are largely unknown. Still, some of these agents prove to be of high ecotoxicity, and for antibiotics, effects not only against veterinary pathogens, but also on other bacteria such as soil microorganisms can be expected. To investigate the effect of antibiotics on soil bacteria, the approach of 'pollution induced community tolerance' or PICT was used. PICT is based on the changes in community composition brought about by exposure to a toxicant. Such changes can include disappearance of the most sensitive species, physiological adaptations, and an increased occurrence of resistant bacteria. As a result, a decreased sensitivity of the total community can be expected. To detect changes in the community tolerance, soils were spiked with three antibiotics and manure and were kept for 3 to 7 weeks. The sensitivity distribution of the microbial communities was analysed before and after exposure of the soils using a functional test based on the metabolization of 31 simple substrates (Biolog® ecoplate). An increasing tolerance of the bacterial communities towards antibiotics was detected. Apart from decreased numbers of bacteria and an overall increase in tolerance, changes especially in the processes with high sensitivity could be found. Statistical analysis of the data was applied to determine the soil concentrations at which negative effects start to occur. Key words: veterinary drugs, antibiotics, soil microorganisms, PICT |
