Abstract

The factors that determine which Helicobacter pylori infected subjects develop duodenal ulcer (DU) are unclear. This study tested the hypothesis that infection density and urease activity are higher in DU than non-DU subjects. Fifty five DU and 55 age and sex matched non-DU subjects were studied. Quantitative methods were used for measuring infection density (viable organism count) and urease activity (Berthelot reaction). DU subjects had a greater antral infection density (geometric mean of colony forming units/mg biopsy protein; 10.5 x 10(5) v 1.3 x 10(5), p < 0.001). They also had higher biopsy urease activity (geometric mean of NH3 nmol/min-1/mg protein-1; 103 v 25, p < 0.001). Urease activity per organism, however, was similar in the two groups showing that high antral urease activity in DU was a reflection of organism density. DU was not present in subjects with an antral infection density less than 10(5) colony forming units/mg protein. A correlation was present between H pylori viable counts and the severity and activity of gastritis. Both severity and activity of gastritis were greater in the antrum of DU compared with non-DU subjects but there was no difference in the body between the two groups. It is concluded that antral H pylori infection density is probably an important determinant of DU development, and that there is a baseline of infection density that is necessary for ulcer formation.