Objective:To investigate the difference in susceptibilities to allitridi of Helicobacter pylori(H.pylori)strains in different gastric diseases and the associations with different genotypes. Methods:H.pylori strains were isolated from gastric antral biopsy specimens and identified.DNA was isolated from H.pylori strains.Different genotypes were determined by polymerase chain reaction(PCR),and the allitridi MICs were determined by agar dilution methods.MIC50 was calculated. Results:The susceptibilities of H.pylori strains varied among different gastric diseases.H.pylori strains in superficial gastritis were significantly more susceptible to allitridi than those in atrophic gastritis(relative median potency was 0.49,95% confidence interval was from 0.24 to 0.80),strains in superficial gastritis were significantly more susceptible than those in gastric cancer(relative median potency was 0.32,95% confidence interval was from 0.06 to 0.68)and strains in atrophic gastritis were significantly more susceptible than those in gastric cancer(relative median potency was 0.16,95% confidence interval was from 0.02 to 0.40).The susceptibilities of H.pylori strains with different genotypes varied among different gastric diseases.In atrophic gastritis,strains with vacAs1+ were significantly more susceptible to allitridi than those with vacAs1-(relative median potency was 0.21,95% confidence interval was from 0.04 to 0.73).In gastric cancer,strains with vacAm1b+ were significantly more susceptible than those with vacAm1b-(relative median potency was 0.07,95% confidence interval was from 0.03 to 0.49). Conclusion:The vacA genotypes play an important role in the susceptibility to allitridi in different gastric diseases.