Helicobacter pylori (Hp) infection causes duodenal ulcers, delays the healing of such ulcers, and is associated with ulcer recurrence. The pathogenic mechanisms involved in Hp-induced duodenal mucosal injury and delay in ulcer healing remain unclear. In this study we sought to investigate the possible pathogenic actions of Hp infection and vacuolating cytotoxin (Vac A) on duodenal epithelial wound healing, using an in vitro wound model consisting of excisionally scraped or eroded IEC-6 duodenal monolayers. Two isogenic strains of Hp were used: wild-type strain 60190, producing Vac A; and an isogenic mutant strain, 60190-v1, that lacks the gene to produce the cytotoxin. The addition of Vac A-positive or Vac A-negative Hp (50:1 ratio of bacterial to epithelial cells) to the eroded or "wounded" IEC-6 monolayers resulted in significant inhibition of wound reepithelialization. The Vac A-positive Hp produced significantly greater inhibition than did the Vac A-negative Hp (70% and 35% inhibition, respectively; P <.001). Additionally, the bacterial supernatant containing Vac A (but not the supernatant lacking the cytotoxin) caused significant inhibition of IEC-6 wound reepithelialization in the absence of Hp infection, indicating that Vac A has an independent inhibitory action on wound reepithelialization. The Vac A inhibition of IEC-6 reepithelialization correlated with down-regulation of actin stress fibers in the migrating cells. Epidermal growth factor (EGF) stimulated IEC-6 wound reepithelialization with a corresponding increase in the formation of actin stress fiber. Vac A-positive bacterial supernatant (but not Vac A-negative supernatant) prevented the EGF-stimulated increase in IEC-6 actin stress fiber formation and wound reepithelialization. These findings demonstrate that Hp infection inhibits the process of duodenal epithelial wound healing. Hp inhibition of duodenal wound healing may therefore be an important pathogenic factor contributing to duodenal mucosal injury and delay in ulcer healing in vivo.