Difloxacin HCl (CAS 91296-86-5) is a small-molecule inhibitor targeting DNA gyrase and topoisomerase IV It is designed to interfere with DNA gyrase-mediated DNA synthesis thereby inhibiting bacterial DNA replication and cell division Difloxacin HCl exerts its biological activity primarily through inhibition of DNA gyrase and topoisomerase IV In cultured human neuroblastoma cells exhibiting multidrug resistance associated protein (MRP)-mediated chemoresistance difloxacin HCl (50 g/ml) increases cell sensitivity to MRP substrates including doxorubicin vincristine daunorubicin and potassium antimony tartrate indicating reversal of the drug-resistance phenotype Based on these pharmacological properties difloxacin HCl holds research potential in antimicrobial susceptibility testing and studies of multidrug resistance reversal