Tuberculosis is a difficult disease to treat; the standard regimen is four antibiotics, rifampicin, isoniazid, pyrazinamide and ethambutol, for six months. An infection that is resistant to both rifampicin and isoniazid is called multi-drug resistant tuberculosis (MDR-TB) and the treatment regimen recommended by the World Health Organization (WHO) is complex but always includes levofloxacin or moxifloxacin, which are fluoroquinolones .