Helicobacter pylori vacA intermediate region i1 strains are associated with more severe histological features of chronic gastritis and increased gastric carcinoma risk in Portugal

Abstract number: P513

Ferreira R.M., Carneiro F., Letley D., Atherton J.C., Figueiredo C.

Background and Aims:H. pylori vacA gene is present in all strains and is polymorphic at the s and m regions. Functionally, s1/m1 strains cause more extensive vacuolation and in a wider range of cell lines than s1/m2 strains, and s2/m2 strains are non-vacuolating. Clinically, s1/m1 strains are associated with gastric atrophy, intestinal metaplasia and gastric carcinoma. Recently, a new polymorphic region within vacA designated intermediate (i) region, was described as a major determinant of vacA toxicity, and i1 strains were associated with gastric carcinoma.

The aim of this study was to characterise the i-region in strains infecting Portuguese patients in order to explore the relationship between i-region genotypes and the histological features of gastritis, and the risk for gastric carcinoma.

Materials and Methods: 154 H. pylori-infected patients were studied, 106 with chronic gastritis and 48 with gastric carcinoma. Histological parameters were scored according to the Sydney system. DNA isolated from gastric specimens was used directly for PCR. Genotypes were determined by reverse hybridisation on a line probe assay for vacA s and m regions, and by type-specific PCR for vacA i region.

Results: vacA i region was successfully genotyped in 97.4% strains. 53 (35.3%) cases were multiple for vacA s, m, or i regions. In the 97 cases of single vacA genotypes, 42 (43.3%) were s1/m1, 45 (46.4%) were s2/m2, and 10 (10.3%) were s1/m2. In agreement with previous descriptions, s1/m1 strains were predominantly i1 (41/42) and only one s1/i2/m1 strain was found. Also, the great majority of s2/m2 strains were i2 (44/45) and a single s1/i2/m1 strain was found. s1/m2 strains were genotyped as i1 (9/10) or i2 (1/10).

In chronic gastritis patients, vacA i1 strains were significantly associated with higher degrees of corpus chronic inflammation and polymorphonuclear activity (P = 0.0006 and P = 0.002, respectively). vacA i1 strains were also associated with the presence of corpus and antral epithelial damage (both P < 0.0001), and with glandular atrophy and intestinal metaplasia (P = 0.0016 and P = 0.0043, respectively). No associations were observed between i region genotypes and H. pylori colonisation density. vacA s1, m1, and i1 strains were strongly associated with gastric carcinoma (all P < 0.0001).

Conclusions:H. pylori vacA i1 strains are associated with more severe histological features of chronic gastritis and increased gastric carcinoma risk in the Portuguese population.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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