DNA hybridization studies of the association of Pseudomonas maltophilia with inflammatory bowel diseases.

An infectious etiology has been suggested for the inflammatory bowel diseases, Crohn's disease and ulcerative colitis, and an association of cell wall-defective variants of Pseudomonas maltophilia and Pseudomonas-like group Va bacteria with Crohn's disease has been reported by Parent and Mitchell. Seven of the Parent-Mitchell isolates were compared by using DNA hybridization and six were identical and similar, but not identical, to a type strain of P. maltophilia. The seventh isolate showed extensive homology with VARC, a reference strain of group Va organism, but not with P. maltophilia. Pseudomonas DNAs were radiolabeled by nick translation and used as probes for homologous DNA in hybridization experiments involving 48 different tissues. The presence of DNA with sequences homologous to those of P. maltophilia was detected in three of 23 Crohn's disease samples, two of 10 ulcerative colitis samples, and none of 15 control samples. There was no hybridization with VARC or Pseudomonas aeruginosa probes. We were unable to culture cell wall-defective organisms from patients' tissues but have detected pleomorphic organisms in hypertonic cultures of 14 of 53 Crohn's disease specimens, none of six ulcerative colitis specimens, and none of 11 control specimens. None reverted to normal bacteria. These results do not support an exclusive association of P. maltophilia with Crohn's disease but rather suggest a possible association of P. maltophilia with IBD. Technical limitations currently preclude definitive conclusions regarding the significance of this association. Although we demonstrated the presence of DNA sequences with homology to P. maltophilia DNA in tissues of some patients with IBD, the role, if any, of these bacteria in the pathogenesis of IBD has yet to be established.