Detection of coccoid Helicobacter pylori: light microscopical immunogold silver enhancing stain

Helicobacter pylori (H. pylori) can be morphologically divided into spiral and coccoid forms. Although many different staining procedures for light microscopy have been developed to detect H. pylori, there are no reports that the coccoid forms can be specially identified by a staining method. The ability to identify the coccoid form of H. pylori by light microscopy would be important for studies evaluating its possible role in gastric disease. We examined whether both the coccoid and the spiral forms could be stained using anti-H. pylori antibody.

Specimens from the stomachs of dyspeptic patients with proven H. pylori infection and H. pylori from culture (1st and 4th day) were stained with the light microscopic immunogold silver enhancing stain using the rabbit IgG specific for H. pylori. Cultured H. pylori was also stained with electron microscopic immunogold staining method using the same antibody. The number of coccoid forms was counted by scanning electron microscopy.

Biopsies and H. pylori from 6 patients were studied. H. pylori from both biopsy material and culture appeared as black organisms by light microscopic immunogold silver enhancing stain. The coccoid forms constituted 0.4% and 98.3% on days 1 and 4 of culture, respectively (by scanning electron microscopy). The antigen recognized by the anti-H. pylori antibody was located on the surface of the flagella, the cell wall, or in the cytoplasm by immunoelectron microscopy.

This study shows that both spiral and coccoid forms of H. pylori can be detected by light microscopic immunogold silver enhancing stain using anti-H. pylori antibody. This simple stain is to be proven useful for studies aimed at understanding whether the coccoid form plays a role in disease.