Eradication of Helicobacter pylori followed by reinfection.

Eradication therapy for Helicobacter pylori is now common, since eradication of this organism reduces the recurrence rate of peptic ulcer. We evaluated the eradication of H. pylori 4 weeks after the cessation of eradication treatment, and encountered recolonization in patients in whom eradication had been confirmed. Using a urease probe, we analyzed the Ure B restriction fragment length polymorphism (RFLP) of the DNA of the recolonized H. pylori by Southern blotting and compared it with that of the H. pylori strain cultured before eradication therapy. RFLP patterns before and after the treatment were identical, indicating that the recolonization of H. pylori was an exacerbation of the primary infection, rather than a reinfection.