Ofloxacin, like other 4-quinolones, is unusual among front line drugs available to treat bacterial infections since it affects bacterial DNA synthesis, rather than cell wall or protein synthesis. The 4-quinolones are also unusual because even for serious infections they can be given orally. Most unusually transferable resistance mediated by plasmids does not affect the 4-quinolone antibacterials. Thus the only way that bacteria can resist these drugs is by chromosomal mutation. However, when mutants gain resistance, they can also lose pathogenicity, and even should mutants remain pathogenic then their resistance cannot transfer to other bacteria by conjugation.