Fumarate reductase is essential for Helicobacter pylori colonization of the mouse stomach

Fumarate reductase (FRD) is the key enzyme in fumarate respiration induced by anaerobic growth of bacteria. In Helicobacter pylori, this enzyme appear s to be constitutively expressed under microaerobic conditions and is not e ssential for its survival in vitro. In this study, the role of FRD in the c olonization of H. pylori was investigated using a mouse model. The frdA gen e coding for subunit A of FRD, and two control genes, copA and copP associa ted with the export of copper out of H. pylori, were inactivated by inserti on of the chloramphenicol acetyltransferase cassette into these individual genes. The isogenic mutants of H. pylori strain AH244 were obtained by natu ral transformation. Seventy-five ICR mice (15 mice/group) were orogastrical ly dosed with either the wild type H. pylori strain AH244, its isogenic mut ants, or Brucella broth (negative control). Five mice from each group were killed at 2, 4 and 8 weeks post-inoculation (WPI), respectively. H. pylori colonization was not detected in mouse gastric mucosa infected with the frd A mutant at any time point in the study by both quantitative culture and PC R. In contrast, the mice inoculated with either wild type AH244, copA or co pP H. pylori mutants became readily infected. These data indicate that FRD plays a crucial role in H. pylori survival in the gastric mucosa of mice. G iven that FRD, present in all H. pylori strains, is immunogenic in H. pylor i-infected patients and H. pylori growth in vitro can be inhibited by three anthelmintics (morantel, oxantel and thiabendazole), this enzyme could pot entially be used both as a novel drug target as well as in the development of vaccines for H. pylori prevention and eradication. (C) 2000 Academic Pre ss.