<qa>  What is the primary purpose of antibiotic therapy?6. Antibiotics for the treatment of Crohns disease eg. ciprofloxacin and metronidazole are allowable but must be discontinued within 12 weeks after surgery. Antibiotics for the treatment of a concomitant infection are allowable throughout the duration of the study as long as the primary purpose of antibiotic therapy is not for the primary treatment of Crohns disease. 