Evaluation of DNA damage in rat lymphocytes exposed to tulathromycin in vitro

Tulathromycin is a relatively new semi-synthetic macrolide antibiotic, a member of the triamilide group, approved primarly for the treatment of respiratory diseases in cattle and swine. Various genotoxicological studies indicated that tulathromycin is not genotoxic, but no available published data originate from the single-cell gel electrophoresis (Comet) assay. Therefore, the objective of this study was to examine whether it can induce primary DNA damage using in vitro Comet assay in isolated rat lymphocytes. Lymphocytes were treated with a broad spectrum of tulathromycin concentrations (from 1 to 100 ? M) and co-treatment with an antioxidant, catalase (100 IU/mL and 500 IU/mL) was performed. The highest concentrations of tulathromycin (50 and 100 ? M) caused significant increase of DNA damage in rat lymphocytes and catalase did not significantly reduce the DNA-damaging effect of tulathromycin. The results of this study indicate that tulathromycin induces genotoxic effects at high concentrations, that catalase does not exert protective effect in this case.