Objective      To clarify the relationship between the diversity of gastric flora and Helicobacter pylori (Hp) infection in the stomach in the Hp-infected Mongolian gerbil.        Methods      A total of 60 Mongolian gerbils were divided into 4 groups

blank control

negative control

direct infection group and pretreatment infection group

with 15 animals in each group. The gerbils in the later group was induced to Mongolian gerbil model with Hp infection by gastric gavage of Hp stain M12

with or without pretreatment of 0.3 ml 50%   ethanol    and 0.3 ml antibiotics suspension. The gastric mucosa samples were collected in 4 weeks later

and the infection rates of Hp were counted at the same time. Total bacterial genomic DNA was collected from the Mongolian gerbils from 4 groups. Samples were analyzed by PCR-denaturing gradient gel electrophoresis (DGGE)

and specific bands on fingerprints were sequenced.       Results      There was a significant difference in the infection rates of Hp between the pretreatment infection group (93.3%) and the direct infection group (26.7%) (P0.05). The average number of bands was 21.6±2.5 in blank control group

3.3±1.1 in negative control group

14.6±2.4 in direct infection group

7.2±2.2 in pretreatment infection group

and there were significant differences among them (P0.05)

which suggested there were significant diversities in gastric flora among 4 groups.        Conclusion       Hp infection is closely related to the changes of composition of gastric flora.