The use of antimycobacterial agents in Crohn's disease.

Seventy-five years ago, a Scottish surgeon, Dalziel, clearly described Crohn's disease (CD) and suggested that it might be caused by a mycobacteria. However, mycobacteria were not isolated from CD tissue until 1978 and 1984. Since then several investigators, using sophisticated polymerase chain reaction (PCR) techniques, found Mycobacterium paratuberculosis sequences in cultures of Crohn's disease tissue in approximately two thirds of patients. Because of a possible mycobacterial etiology, Rutgeerts et al. (J Clin Gastroenterol 1992;15:24-8) treated resected ileocolonic CD patients who had early evidence of recurrence with ethambutol and rifabutin. Patients were followed by colonoscopy to observe changes in the intestinal lesions, but no improvement was noted. Rutgeerts et al. concluded that antimycobacterial therapy did not affect the course of CD. Failure of these antibiotics does not necessarily negate the mycobacterial theory of CD, however. The study population of Rutgeerts et al. was too small, and the treatment period too short. Furthermore, ethambutol shows little or no activity against the proposed Crohn's organism, Mycobacterium paratuberculosis; use of only one active agent (rifabutin) can lead to drug resistance and failure of antibiotic therapy. We hope that Rutgeerts et al. will continue these important studies, but with a more active combination of antimycobacterial drugs for a longer time.