title: Toxicity of five antibiotics and their mixtures towards photosynthetic aquatic organisms: implications for environmental risk assessment.
abstract: The individual and combined toxicities of amoxicillin, erythromycin, levofloxacin, norfloxacin and tetracycline have been examined in two organisms representative of the aquatic environment, the cyanobacterium Anabaena CPB4337 as a target organism and the green alga Pseudokirchneriella subcapitata as a non-target organism. The cyanobacterium was more sensitive than the green alga to the toxic effect of antibiotics. Erythromycin was highly toxic for both organisms; tetracycline was more toxic to the green algae whereas the quinolones levofloxacin and norfloxacin were more toxic to the cyanobacterium than to the green alga. Amoxicillin also displayed toxicity to the cyanobacterium but showed no toxicity to the green alga. The toxicological interactions of antibiotics in the whole range of effect levels either in binary or multicomponent mixtures were analyzed using the Combination Index (CI) method. In most cases, synergism clearly predominated both for the green alga and the cyanobacterium. The CI method was compared with the classical models of additivity Concentration Addition (CA) and Independent Action (IA) finding that CI could accurately predict deviations from additivity. Risk assessment was performed by calculating the ratio between Measured Environmental Concentration (MEC) and the Predicted No Effect Concentration (PNEC). A MEC/PNEC ratio higher than 1 was found for the binary erythromycin and tetracycline mixture in wastewater effluents, a combination which showed a strong synergism at low effect levels in both organisms. From the tested antibiotic mixtures, it can be concluded that certain specific combinations may pose a potential ecological risk for aquatic ecosystems with the present environmentally measured concentrations.
authors: Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid, Spain.
authors: Miguel
authors: M
authors: González-Pleiter
authors: Soledad
authors: S
authors: Gonzalo
authors: Ismael
authors: I
authors: Rodea-Palomares
authors: Francisco
authors: F
authors: Leganés
authors: Roberto
authors: R
authors: Rosal
authors: Karina
authors: K
authors: Boltes
authors: Eduardo
authors: E
authors: Marco
authors: Francisca
authors: F
authors: Fernández-Piñas
mesh_terms: D000658:Amoxicillin / Q000032:analysis / Q000633:toxicity; D017033:Anabaena / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000032:analysis / Q000633:toxicity*; D059001:Aquatic Organisms / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D000460:Chlorophyta / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D004355:Drug Stability; D004357:Drug Synergism; D004917:Erythromycin / Q000032:analysis / Q000633:toxicity; D024841:Fluoroquinolones / Q000032:analysis / Q000633:toxicity; D005618:Fresh Water / Q000737:chemistry; D020128:Inhibitory Concentration 50; D010788:Photosynthesis / Q000187:drug effects*; D010839:Phytoplankton / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D018570:Risk Assessment; D013030:Spain; D013752:Tetracycline / Q000032:analysis / Q000633:toxicity; D018675:Toxicity Tests; D062065:Wastewater / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*; D060753:Water Quality
chemical_list: D000658:Amoxicillin; D000900:Anti-Bacterial Agents; D004917:Erythromycin; D024841:Fluoroquinolones; D013752:Tetracycline; D062065:Wastewater; D014874:Water Pollutants, Chemical