Search for Mycobacterium paratuberculosis DNA in orofacial granulomatosis and oral Crohn's disease tissue by polymerase chain reaction

Background-Although intestinal Crohn's disease has long been suspected to have a mycobacterial cause, possible mycobacterial involvement in orofacial granulomatosis (OFG) and oral lesions of Crohn's disease has not yet been investigated. Aims-As the slow growing Mycobacterium paratuberculosis has been implicated in the aetiology of intestinal Crohn's disease, the potential involvement of this mycobacterial species in OFG and oral lesions of Crohn's disease was investigated. Patients-To attempt detection of the organism in OFG and oral Crohn's disease tissue samples, a polymerase chain reaction (PCR) assay was used on archival formalin fixed, paraffin wax embedded oral tissue sections from 30 patients with OFG, seven with Crohn's disease, and 12 normal controls. Methods-The PCR assay used was based on primers targeting the 5' region of the multicopy IS900 DNA insertion element of the M paratuberculosis genome. In order to achieve maximum sensitivity, two rounds of PCR were carried out and amplicons confirmed by Southern blot hybridisation to a digoxigenin labelled IS900 DNA probe. Results-None of the OFG and oral lesions of Crohn's disease samples were positive for M paratuberculosis and all normal controls were also negative. Conclusions-These results suggest that M paratuberculosis may not be a major aetiological agent in OFG or oral Crohn's disease lesions, although the use of paraffin wax embedded tissue as opposed to fresh tissue as a sample source could underestimate the true prevalence of the organism.