Detection of invasive in dogs with granulomatous colitis using immunohistochemistry.

Granulomatous colitis in dogs can be associated with infection of the colonic mucosa by invasive strains of . To date, fluorescence in situ hybridization (FISH) is the gold-standard method to assess intramucosal and intracellular bacterial invasion. However, FISH requires expensive fluorescence microscopy equipment and is therefore not widely available. We investigated the use of immunohistochemistry (IHC) as an alternative method to detect invasive in dogs with granulomatous colitis. Archived paraffin-embedded blocks were selected from 26 dogs with colitis, in which FISH had been performed by an outside laboratory. Using a polyclonal antibody, IHC for was performed on sections cut from the same blocks, and the presence of invasive was recorded. All 11 specimens in which FISH had detected were also positive on IHC, with strong immunolabeling in the cytoplasm of macrophages and extracellularly in the lamina propria; all 15 specimens that were negative for invasive bacteria on FISH were also negative on IHC. We found that IHC is a sensitive technique for the detection of invasive in dogs with granulomatous colitis.