The histological parameters of Helicobacter pylori (H. pylori) gastritis are dependent on the virulence factor profile of the microbe, which includes the cytotoxins vacA (vacuolating cytotoxin A) and cagA (cytotoxinassociated gene A) as well as the duration of infection. The virulence factor genotypes vacA and cagA were assessed by the line probe reverse hybridization assay INNO-LiPA and correlated with the histological parameters of H. pylori infection, in particular intestinal metaplasia (IM) as well as with the patient's age. A total of 120 patients were analyzed; 47 patients with IM in the antrum and 73 control patients without this alteration. The vacA s1 cagA þ genotype (high virulence) correlated with the presence of antral IM, a more intense acute inflammation in both antrum and corpus and the formation of ulcer. The vacA m1 genotype (high virulence) correlated with a more intense acute inflammation in only the corpus as well as more prominent Russell bodies in the antrum. H. pylori strains with the vacA s2 m2 cagAÀ genotype (low virulence) were rarely found in these conditions (all P o0.05). No correlation with the virulence status was found for the type and extent of IM, the intensity of chronic inflammation, the formation of lymphoid follicles and the microbial density. Furthermore, patients with IM were 7 years older than their counterparts without (Po0.05). Finally, there was a trend for more virulent vacA s1 m1 cagA þ strains to be found in younger individuals (P40.05). The virulence genotype of the microbe is an important determinant for the severity of the gastritis and the formation of antral IM. Age is an additional factor for the development of IM. Keywords: Helicobacter; virulence; gastritis; histology; resistance The Gram-negative bacteria Helicobacter pylori colonize the human stomach. 1 Prolonged infection is associated with several diseases like chronic gastritis, peptic ulcer disease and stomach carcinoma or lymphoma. This association depends on bacterial, host and environmental factors. Among the bacterial factors, several virulence proteins determine the severity of inflammation and the formation of intestinal metaplasia (IM). [2][3][4][5] The most studied virulence proteins are vacA and cagA, which are injected into the gastric epithelial cell through a multimeric protein complex. 6 This protein complex is elaborated from the PAI (pathogenicity-island), a 40 kb DNA segment. CagA makes part of the PAI and targets particularly the phosphorylation cascade and the tight junctions. 7-9 H. pylori are either cagA-positive or -negative. VacA, present in all H. pylori, is located outside the PAI and forms an oligomeric pore with channel activity. 10,11 VacA has two variable parts: The s (signal peptide) region exists as allele s1 or s2. The m (middle) region occurs as m1 or m2 allelic type. The allele combination s1 m1 confers high, s1 m2 intermediate and s2 m2 low toxin activity. Most vacA s1 strains are cagA-positive, thus the two markers are closely related. 12 H. pylori infection is normal...