AVIRULENT, UREASE-DEFICIENT HELICOBACTER-PYLORI COLONIZES GASTRIC EPITHELIAL EXPLANTS EX-VIVO

Background: Urease-negative Helicobacter pylori generated by insertional mutagenesis fails to colonize gnotobiotic piglets, and this effect is largely independent of gastric pH. The purpose of this study was to determine whether urease-negative H. pylori colonizes gastric explants ex vivo. Methods: Gastric mucosal explants derived from neonatal germ-free piglets were inoculated with either wild-type H. pylori or one of two mutants derived by insertional mutagenesis. Results: All three bacterial strains colonized explants. The level of colonization increased over the duration of the experiment, reaching 10(8)-10(9) cfu/g gastric mucosa by 72 h after inoculation. Morphologic evidence of colonization was similar to that observed in gnotobiotic piglets. Conclusions: Colonization of explants was not affected by lack of urease. These results contrast with previous findings showing that urease activity is essential for colonization of piglets by H. pylori. Thus, urease-dependent colonization is dependent on an intact gastric microenvironment.