title: Effects of six antibiotics and their binary mixtures on growth of Pseudokirchneriella subcapitata.
abstract: The effect of ampicillin (AMP), amoxicillin (AMX), cephalotin (CEP), ciprofloxacin (CPF), gentamycin (GEN), and vancomycin (VAN) have been examined individually and as binary mixtures, on a non-target aquatic organism, the green alga Pseudokichneriella subcapitata. The β-lactam antibiotics AMP and AMX were not toxic to the alga at concentrations up to 2000 mgl(-1) (less than 10% of algal growth inhibition), whereas the fluoroquinolone CPF, and the aminoglycoside GEN were the most toxic antibiotics, with an EC50=11.3 ± 0.7 mgl(-1) and 19.2 ± 0.5 mgl(-1), respectively. The cephalosporin CEP and the glycopeptide VAN were less toxic than the last two mentioned, showing an EC50>600 mgl(-1) and 724 ± 20 mgl(-1), respectively. The toxicological interactions of binary mixtures were predicted by the two classical models of additivity: concentration addition (CA) and independent action (IA), and compared to the experimentally determined toxicities over a range of concentrations between 1 and 50 mgl(-1). In all cases a clear synergistic effect was observed, showing that single compound toxicity data are not adequate for the prediction of aquatic toxicities of antibiotic mixtures. Risk assessment was performed by calculating the ratio between predicted environmental concentrations (PEC) and the predicted no effect concentration (PNEC). All the antibiotics tested, excepting GEN, have a potential ecological risk, taking into account the PEC of hospital effluents from Buenos Aires, Argentina. These risks increase when antibiotics are present in binary mixtures.
authors.affiliation: Cátedra de Higiene y Sanidad, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 4° Piso, C1113AAC Buenos Aires, Argentina. Electronic address: amagda@ffyb.uba.ar.
authors.forename: A
authors.initials: A
authors.lastname: Magdaleno
authors.affiliation: Cátedra de Higiene y Sanidad, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 4° Piso, C1113AAC Buenos Aires, Argentina.
authors.forename: M E
authors.initials: ME
authors.lastname: Saenz
authors.affiliation: Departamento de Biodiversidad y Biología Experimental y Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA-CONICET), Buenos Aires, Argentina.
authors.forename: A B
authors.initials: AB
authors.lastname: Juárez
authors.affiliation: Cátedra de Higiene y Sanidad, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junin 956, 4° Piso, C1113AAC Buenos Aires, Argentina.
authors.forename: J
authors.initials: J
authors.lastname: Moretton
mesh_terms: D000900:Anti-Bacterial Agents / Q000633:toxicity*; D000460:Chlorophyta / Q000187:drug effects* / Q000254:growth & development; D004347:Drug Interactions; D018570:Risk Assessment
chemical_list: D000900:Anti-Bacterial Agents
keywords: Antibiotic toxicity; Green algae; Mixture toxicity; Risk quotient; Synergism