TA5 Ecotoxicity and Environmental Chemistry of Antibiotics
Room 17A/B, Level 4
8:00 AM - 12:00 PM, Tuesday, 11 November 2003
Chair: Aga, Diana ,
(204) The effects of pharmaceuticals on freshwater sediment bacterial communities.
Warne, A1, Sibley, P1, 1 Centre for Toxicology, University of Guelph
ABSTRACT- We used community-level physiological profiling (CLPP) to evaluate the functional response of sediment microbial communities to a mixture of 8 pharmaceuticals (acetominophen, sulfamethoxazole, caffeine, trimethoprim, fluoxetine, levofloxacin, atorvastin, carbamazepine) and the antibiotic Tylosin. In the mixture study, 5 treatments, ranging in total concentration from 10 (low) - 4000 (ultra-high) ug/L were applied to triplicate microcosms twice weekly. Samples were collected at –1, 2, 14, 28, and 52 d. In the Tylosin study, concentrations of 0, 10, 30 and 300 ug/L were applied to triplicate microcosms, while concentrations of 600, 1000 and 3000 ug/L were applied to single microcosms. Samples were collected at –1, 7, 14, 28, and 35 d. In both studies, microorganisms were immediately extracted and inoculated into the plates (one/microcosm) and readings taken every 24 hrs for 1 wk. Based on Shannon Diversity Index results, Tylosin had a negative effect on the diversity of the sediment microbial community at concentrations >300 ug/L after 28 d. This impact was also reflected in the principal components analysis of carbon utilization patterns indicated by as a divergence of these high treatments away from the primary cluster, which represented the unimpaired condition. In the mixture study, the microbial community was impacted at the medium, high and ultra high levels after 28 d, showing a trend similar to that exhibited by Tylosin. Because these compounds do not occur at concentrations at which effects were observed, they do not appear to pose an immediate risk to the functional diversity of freshwater sediment ecosystems. Tylosin and chlortetracycline were also assessed for their impact on nitrification using a laboratory microcosm assay. Preliminary results indicate a clear dose-response relationship with Tylosin at environmentally relevant concentrations, and to a lesser extent chlortetracycline.
Key words: antibiotics, microcosm, bacterial community, community level physiological profiling (CLPP)