AIM:To establish a stable and reliable model of Helicobacterpylori infection model in Mongolian gerbils and to observepathological changes in gastric mucosa in infected animals.METHODS:Mongolian gerbils were randomly divided into18 groups;6 groups were infected with Hpyloriclinical strainY06 (n=6,groups Y),6 groups were infected with Hpyloristrain NCTC11637 (n=6,groups N),and 6 uninfected groupsas negative controls (n=4,groups C).Hpylorisuspensionsat the concentrations of 2×10~8 and 2×10~9 CFU/mL of strainNCTC11637 and strain Y06 were prepared.The animals inthree groups N and in three groups Y were orally challengedonce with 0.5 mL of the low concentration of the bacterialsuspension.The animals in another three groups N and inanother three groups Y were orally challenged with 0.5 mlof the high concentration of the bacterial suspension for 3times at the intervals of 24 h,respectively.For the negativecontrols,the animals in six groups C were orally givenwith the same volume of Brucella broth at thecorresponding inoculating time.The animals were killedafter 2nd,4~(th) and 6~(th) week after the last challenge andthe gastric mucosal specimens were taken for urease test,bacterial isolation,pathological and immunohistochemicalexaminations.RESULTS:Positive isolation rates of Hpyloriin the animalsof groups Y at the 2nd,4~(th) and 6~(th) week after one challengewere 0%,16.7% and 66.7%,while in the animals of groupsN were 0%,0% and 16.7%,respectively.Positive isolationrates of Hpyloriin the animals of groups Y at the 2nd,4~(th)and 6~(th) week after three challenges were 66.7%,100%and 100%,while in the animals of groups N were 66.7%,66.7% and 100%,respectively.In animals with positiveisolation of Hpylori,the bacterium was found to colonizedon the surface of gastric mucosal cells and in the gastricpits,and the gastric mucosal lamina propria was infiltratedwith inflammatory cells.CONCLUSION:By using H pylori suspension at highconcentration of 2×10~9 CFU/mL for multiple times,the orallychallenged Mongolian gerbils can be used as a stable andreliable H pylori infection model.The 2 strains of H pylorican colonize in gastric mucosa of the infected animals and cause mild inflammation reaction. AIM: To establish a stable and reliable model of Helicobacter pylori infection model in Mongolian gerbils and to observepathological changes in gastric mucosa in infected animals. METHODS: Mongolian gerbils were randomly divided into18 groups; 6 groups were infected with Hpyloriclinical strainY06 (n = 6, groups 6 groups were infected with Hpyloristrain NCTC11637 (n = 6, groups N), and 6 uninfected groupsas negative controls (n = 4, groups C) .Hpylorisuspensionsat the concentrations of 2 × 10 ~ 8 and 2 × 10 ~ 9 CFU / mL of strain NCTC11637 and strain Y06 were prepared. The animals inthree groups N and in three groups Y were orally challengedonce with 0.5 mL of the low concentration of the bacterialsuspension. The animals in another three groups N and inother three groups Y were orally challenged with 0.5 mlof the high concentration of the bacterial suspension for 3 times at the intervals of 24 h, respectively. For the negativecontrols, the animals in six groups C were orally givenwith the same volume of Brucella broth at thecorresponding inoculating time. The animals were killed after 2nd, 4 th (th) and 6 th (th) weeks after the last challenge and the gastric mucosal specimens were taken for urease test, bacterial isolation, pathological and immunohistochemicalexaminations.RESULTS: Positive isolation rates of Hpylori in the animals of groups Y at the 2nd, 4 th (th) and 6 th (th) weeks after one challenge were 0%, 16.7% and 66.7% while in the animals of groups N were 0%, 0% and 16.7% respectively. Positive isolation rates of Hpylori in the animals of groups Y at the 2nd, 4 th (th) and 6 th (th) weeks after three challenges were 66.7%, 100% and 100%, while in the animals of groups N were 66.7% , 66.7% and 100% respectively. In animals with positive isolation of Hpylori, the bacterium was found to colonizedon the surface of gastric mucosal cells and in the gastric pits, and the gastric mucosal lamina propria was infiltrated with inflammatory cells. CONCLUSION: By using H pylori suspension at high concentration of 2 × 10 ~ 9 CFU / mL for multiple times, t heorallychallenged Mongolian gerbils can be used as a stable andreliable H pylori infection model. 2 strains of H pylorican colonize in gastric mucosa of the infected animals and cause mild inflammation reaction.