 This mechanism can also affect mammalian cell replication.In particular, some congeners of this drug family (for example those that contain the C-8 fluorine), display high activity not only against bacterial topoisomerases, but also against eukaryotic topoisomerases and are toxic to cultured mammalian cells and "in vivo" tumor models.Although quinolones are highly toxic to mammalian cells in culture, its mechanism of cytotoxic action is not known.