TYPING OF HELICOBACTER-PYLORI VACA GENE AND DETECTION OF CAGA GENE BYPCR AND REVERSE HYBRIDIZATION

The present report describes an analysis of two virulence genes of Hel icobacter pylori. Parts of the cagA gene, as well as parts from the si gnal (s) and middle (m) regions of the mosaic vacA gene, were amplifie d with biotin-labelled PCR primers and the products were subsequently analyzed by a single-step reverse hybridization line probe assay (LiPA ). This assay comprises a strip containing multiple specific probes fo r the vacA s region (s1a, s1b, and s2 alleles), the, vac4 m region (m1 and m2 alleles), and the cagA gene. A total of 103 H. pylori-positive materials, including cultured isolates, gastric biopsy specimens, and surgical specimens from patients living in Portugal (n = 55) and The Netherlands (n = 48) were tested by the PCR-LiPA. cagA was detected in 83 and 73% of the Portuguese and Dutch patients, respectively. vacA t yping results, as determined by reverse hybridization, were completely concordant with those of sequence analysis. Most Portuguese patients (72%) contained type s1b, whereas most Dutch patients (61%) contained type s1a (P < 0.001). The method is also very effective at detecting t he presence of multiple genotypes in a single biopsy specimen. The pre valence of multiple strains in Portuguese patient samples was signific antly higher (29%) than that in Dutch patient samples (8%) (P = 0.001) . There was a significant association between the presence of ulcers o r gastric carcinoma and the presence of vacA type s1 (s1a or s1b; P = 0.008) and cagA (P = 0.003) genes.