Toxicological and genotoxic assessment of three veterinary antibiotics on green algae and Allium cepa

MAGDALENO, ANAHI; CARUSSO, SOFIA; MORETTON, JUAN

Curitiba

Congreso; XIV Congresso Brasileiro de Ecotoxicologia; 2016

Sociedade Brasileira de Ecotoxicologia

Antibiotics are used in veterinary medicine to treat and prevent disease, and for growth promotion in food animals. A large percentage of antibiotics are excreted without being metabolized, reaching soils through manure application, and eventually surface waters after rainfall events. Some antibiotic agents can be persistent in the environment and could have negative effects on the non-target organisms. The aim of this work was to analyze the toxicity and genotoxicity of three veterinary antimicrobials commonly used in beef cattle production (chlortetracycline, oxytetracycline and enrofloxacin) on aquatic green algae (Pseudokirchneriella subcapitata and Ankistrodesmus fusiformis) and on the terrestrial plant Allium cepa.According to the algal bioassays, the three antibiotics analyzed showed toxicity to the two species test. The EC50 values obtained for the antibiotics CTC, OTC and ENF were 2.30 (0.15-3.10), 1.70 (0.20-4.00) and 2.50 (1.70-7.70) mg/L in P. subcapitata, respectively, and 6.90 (4.10-14.30), 8.50 (6.30-20) and 16.50 (10.30-16.70) mg/L in A. fusiformis, respectively. These results are consistent with the data from literature. Authors that followed comparable standardized test methods using green algae tests reported similar result: Holten-Lützhøft et al. (1999) found the OTC EC50 of 4.5 (2.3?8.6) mg/L, while Eguchi et al. (2004) and van der Grinten et al. (2010) report values of 0.34 (0.32?0.36) mg/L and 0.6 (0.56?0.62) mg/L, respectively. On the other hand, the EC50 values for enrofloxacin and their degradation sub-product, ciprofloxacin, is in the range of 3.10?18.70 mg/L for green algae (Robinson et al., 2005; Ebert et al., 2011). The native species A. fusiformis showed lower sensitivity to the antibiotics than P. subcapitata.The continual introduction of these veterinary compounds in soil, through repeated manure application, may eventually build up their concentration high enough to enter the terrestrial environment as a potent threat. Until now there are few information about toxicity or genotoxicity of antibiotics on plants. In order to evaluate the genotoxic effects of CTC, OTC and ENF on plants, the A. cepa test was carried out. Two negative controls were tested: distilled water for CTC, and DMSO (1% v/v) for OTC and ENF. The MI (%) values in these controls were 63.47±9.77 and 65.49±2.93, respectively. The MI (%) values obtained in CTC (100 mg/L), OTC (10 mg/L) and ENF (10 mg/L) were between 66.94±5.62 and 67.00±10.00, showing no significant differences with respect to the controls and the absence of cytotoxicity. The genotoxic parameters CA and MN also showed no significant differences between the negative controls and the antibiotics concentrations. The values of CA (%) and MN (%) in the controls were the follows: CA in distilled water = 0.09±0.17, CA in DMSO = 0.29±0.15, MN in distilled water = 0.55±0.66, MN in DMSO = 0.34±0.13. The CA and MN in CTC were 0.04±0.05 and 0.35±0.14, respectively. On the other hand, the CA and MN in OTC and ENF were between 0.04±0.06 and 0.32±0.22 mg/L, and between 0.36±0.14 and 0.55±0.31 mg/L, respectively. In the presented study the antimicrobials chlortetracycline (CTC), oxytetracycline (OTC) and enrofloxacin (ENF) were tested according to standard conditions on toxicity and genotoxicity to aquatic green algae and the terrestrial higher plant Allium cepa, respectively. The results indicated that the three antibiotic compounds were toxic to green algae at concentrations between 0.15 to 20 mg/L, being the standard species P. subcapitata more sensitive than the Argentine native species, A. fusiformis. On the other hand, these antimicrobial agents were no cytotoxic nor genotoxic to A. cepa.