Ecotoxicity of five veterinary antibiotics on indicator organisms and water and soil communities

This study explores the environmental effects of five common veterinary antibiotics widely detected in the environment, (chlortetracycline,CTC; oxytetracycline,OTC; florfenicol,FF; neomycin, NMC; and sulfadiazine, SDZ) on four bioindicators: Daphnia magna, Vibrio fischeri, Eisenia fetida, and Allium cepa, representing aquatic and soil environments. Additionally, microbial communities characterized through 16 S rRNA gene sequencing from a river and natural soil were exposed to the antibiotics to assess changes in population growth and metabolic profiles using Biolog EcoPlates™. Tetracyclines are harmful to Vibrio fisheri (LC₅₀ ranges of 15-25 µg/mL), and the other three antibiotics seem to only affect D. magna, especially, SDZ. None of the antibiotics produced mortality in E. fetida at concentrations below 1000 mg/kg. NMC and CTC had the highest phytotoxicities in A. cepa (LC₅₀ = 97-174 µg/mL, respectively). Antibiotics significantly reduced bacterial metabolism at 0.1-10 µg/mL. From the highest to the lowest toxicity on aquatic communities: OTC > FF > SDZ ≈ CTC > NMC and on edaphic communities: CTC ≈ OTC > FF > SDZ > NMC. In river communities, OTC and FF caused substantial decreases in bacterial metabolism at low concentrations (0.1 µg/mL), impacting carbohydrates, amino acids (OTC), and polymers (FF). At 10 µg/mL and above, OTC, CTC, and FF significantly decreased metabolizing all tested metabolites. In soil communities, a more pronounced decrease in metabolizing ability, detectable at 0.1 µg/mL, particularly affected amines/amides and carboxylic and ketonic acids (p < 0.05). These new ecotoxicity findings underscore that the concentrations of these antibiotics in the environment can significantly impact both aquatic and terrestrial ecosystems.