VIRULENCE-ASSOCIATED GENES AS MARKERS OF STRAIN DIVERSITY IN HELICOBACTER-PYLORI INFECTION

To establish a marker of strain diversity of Helicobacter pylori, a ge netic examination was performed based on the detection rates by PCR of cagA and vacA, which are known to be virulence-associated genes. The test strains were obtained from 70 patients suffering from gastric ulc er (GU), 82 patients with duodenal ulcer (DU) and 48 patients with gas tritis (GS). Fragments located in the three different regions of vacA were amplified; V1 being the upstream portion, V2 the mid-portion and V3 the downstream portion. For cagA, the detection rates were 70% for GU, 79% for DU and 50% for GS, showing a significantly higher rate for DU than for GS (P = 0.0005). With V1, the detection rates were 90% fo r DU, 90% for DU and 69% for GS, giving a significantly higher rate fo r GU than for GS (P = 0.0036) and also giving a significantly higher r ate far DU than for GS (P = 0.0019). With V2, the detection rates were 60% fur GU, 70% for DU and 44% for GS, giving a significantly higher rate for DU than for GS (P = 0.0024). The differences in vacA gene pol ymorphism were closely related to the evidence of gastroduodenal ulcer s in H. pylori infection, Furthermore, the detection rates of cagA and polymorphisms of vacA by PCR could be used as markers of strain diver sity in H. pylori-induced gastroduodenal ulcer.