Helicobacter pylori reinfection is virtually absent after successful eradication.

This study examined whether reinfection or recrudescence accounts for the reappearance of Helicobacter pylori infection after apparent successful eradication. In a prospective study, 173 patients cured from H. pylori infection underwent follow-up endoscopies, with biopsies for culture and histopathology, every 3 months during the first year after treatment. Subsequently, elective half-yearly endoscopies were performed in 124 patients; the remaining 49 underwent follow-up endoscopy only in 1995. At reappearing infection, DNA profiles of pretreatment and recurrent strains were compared. After 3.5 years (range, 1.0-9.2), H. pylori infection recurred in 9 patients (5.2%). Reappearing infections were classified as endoscopically transmitted reinfection (n = 2), unclassified because of loss of pretreatment isolate (n = 1), or recrudescence (identical DNA patterns before and after treatment; n = 6). The reappearance rate of infection, discarding endoscopic transmission, was 1.2% (7/601 H. pylori-negative patient-years). There was virtually no reinfection with H. pylori after eradication in this adult Western population. These data do not rule out acquisition of H. pylori.