Ecotoxicity of mixtures of antibiotics used in aquacultures

• Published in: Environmental toxicology and chemistry 2006-08, Vol.25 (8), p.2208-2215
• Main Authors: Christensen, Anne Munch, Ingerslev, Flemming, Baun, Anders
• Format: Article
• Language: English
• Subjects: Activated sludge; Algae; Aliivibrio fischeri - drug effects; Aliivibrio fischeri - genetics; Animal, plant and microbial ecology; Anti-Bacterial Agents - toxicity; Antibiotics; Applied ecology; Aquaculture; Aquatic ecosystems; Aquatic environment; Bacterial community; Bacterial proteins; Bioassays; Biological and medical sciences; Chemicals; DNA Replication - drug effects; Ecosystem; Ecotoxicology, biological effects of pollution; Eukaryota - drug effects; Freshwater organisms; Fundamental and applied biological sciences. Psychology; General aspects; Isobolograms; Microbial ecology; Microorganisms; Mixture toxicity; Protein synthesis; Pseudokirchneriella subcapitata; Sewage; Statistical analysis; Statistical methods; Synergistic effect; Test organisms; Tests; Toxicity; Various environments (extraatmospheric space, air, water); Vibrio fischeri; Water Pollutants, Chemical - toxicity
• ISSN: 0730-7268; 1552-8618
• DOI: 10.1897/05-415R.1

More or less well‐defined mixtures of antibiotics used in aquacultures may be distributed in the aquatic environment. Therefore, a systematic mixture ecotoxicity study was performed with the aquaculture antibiotics oxytetracycline, oxolinic acid, erythromycin, florfenicol, and flumequine. Test organisms were freshwater algae (Pseudokirchneriella subcapitata), activated sludge microorganisms, and luminescent bacteria (Vibrio fischeri). Design and statistical analysis of test results were based on isobolographic analysis. Synergistic effects were observed when combinations of erythromycin and oxytetracycline were tested on activated sludge microorganisms, and in these cases model predictions indicate independent action on the different bacterial species in the sludge. As predicted from the modes of action, concentration addition was evident when flumequine and oxolinic acid were mixed and tested on sludge bacteria. In the algae test, the combined toxicity of antibiotics could not be predicted based on knowledge of the modes of action of the individual compounds. Independent of the test species, our results gave examples of combined effects that were higher than predicted based on the assumption of concentration addition. This result underlines the need to consider the effects of mixtures of antibiotics on environmental organisms. The isobolographic method appears to be a suitable tool for this purpose, particularly for well‐defined mixtures with few substances.