The association between Campylobacter-like organisms (CLOs) and lesions of the gastric mucosa was studied in 59 consecutive biopsies. Hematoxylin and eosin and Warthin-Starry silver stains, as well as high-resolution light microscopy (HRLM) and transmission electron microscopy (TEM), were used. The organisms were found in intimate contact with foveolar cells showing abundant phagolysosomes and alterations of the intercellular complexes. CLOs also were seen in close proximity of parietal cells in resting phase, some of which showed degenerative changes. The findings are discussed in light of recent reports linking CLOs to the cause of gastritis. (Key words: Campylobacter; Ultrastructure; Gastritis; Peptic ulcer; Parietal cells; Fovelor cells). Am J Clin Pathol 1986; 86: 575-582 SPIRAL MICROORGANISMS have been reported in the gastric mucosa since 1940, 3 but their possible role as pathogens has not been clarified. Recently, these organisms have been found to share many characteristics with the Campylobacter genus, and the term Campylobacterlike organisms (CLOs) has been widely used in referring to them.8 It has been postulated that these organisms may play an etiologic role in peptic ulcer disease, and a hypothetical mechanism has been offered to explain that role.9 This study was conducted to provide morphologic and bacteriologic data on the infection of the gastric mucosa with CLOs and to explore possible mechanisms responsible for lesions and symptoms. Materials and MethodsBiopsies from the gastric antrum and corpus were taken from 59 consecutive patients attending the endoscopy clinic at Charity Hospital in New Orleans between March and September 1985. One tissue fragment was fixed in buffered formalin, embedded in paraffin, and sectioned and stained with hematoxylin and eosin and WarthinStarry silver technics. A second fragment was used for high-resolution light microscopy (HRLM); if CLOs were identified (33 cases), the block was further processed for Departments of Pathology and Internal Medicine (Gastroenterology), Louisiana State University MedicalCenter, New Orleans, Louisiana transmission electron microscopy (TEM) according to methods described previously. 5 In 23 cases, a third tissue fragment was used to prepare smears for Gram's stain and for bacteriologic cultures.For HRLM and TEM, intact biopsies from antrum and corpus were immediately fixed in paraformaldehyde and postfixed in osmium tetroxide according to previously described standard methods.5 After dehydration, the tissue was embedded in Spurr's epoxy, and l-/um sections were cut for HRLM. They were stained with toluidine blue and counterstained with basic fuchsin. This method allowed the microorganisms to be readily recognizable. Four TEM grids per block were stained with uranyl acetate and lead citrate and studied in a Zeiss® electron microscope. The presence of CLOs and their relationship with normal cells was assessed. A systematic search for the presence of microorganisms and for degenerative changes in the epithelial cells was made. Bo...