In situ identification of mycobacteria in Crohn's disease patient tissue using confocal scanning laser microscopy

The diversity in the methodology employed to investigate Crohn's disease (CD) etiology has added significantly to the controversy of the mycobacterial role in this chronic inflammatory bowel disease. Mycobacterium avium subsp paratuberculosis (MAP), a proposed and suspected agent in many CD patients, is a fastidious and very slow grower bacillus, which causes Johne's disease (JD) in cattle. The methodology that has been widely and successfully used for isolation and identification of MAP from and in JD animals is not reliable and has proven to be unsuccessful in achieving the same objectives for CD diagnosis. In this study, a Confocal Scanning Laser Microscopy (CSLM) system has been employed in an attempt to detect MAP in CD patient. In situ hybridization was performed on full thickness tissue using rabbit anti-MAP polyclonal antibody that was adsorbed with E. coli protein extracts. Consequently, MAP was detected in the microvilli region in tissue specimens from CD patient and not in the controls. In the same CD tissue specimen, MAP was not detected when isotype normal rabbit sera was employed. The polyclonal antibody marker may be replaced with monoclonal antibodies, if available, or with MAP-specific-DNA or RNA probes. This technique adds an additional approach to investigate MAP role in CD etiology especially when the culture approach is long and inconsistent.