摘要目的 探讨产毒性大肠杆菌（ETEC）毒力受环境因素调控的机理。方法 采用ELISA及DNA-RNA杂交法观察在不同培养条件下，ETEC毒力因子及毒力基因mRNA的表达；并且比较加入或不加入DNA解旋酶抑制剂novobiocin和coumermycinA1对ETEC毒力因子及其基因mRNA表达的影响。结果 ETEC肠毒素(LT和ST)及定居因子(CFA)表达均与mRNA呈剂量反应关系；novobiocin和coumermycinA1对ETEC生长的影响也受细菌培养环境的影响；在正常培养条件下，novobiocin或coumermycinA1对ETEC的生长有轻微抑制作用，毒力的表达也相对较低，但在培养环境改变时，如：在novobiocin20μg/ml或coumermycinA12μg/ml的作用下，LT、ST和CFA的表达均明显增加，mRNA的表达也明显增高。结论 环境刺激可能通过影响ETEC染色体DNA毒力调控基因的超螺旋结构而调控ETEC毒力的表达。

abstractsObjective To analyze the mechanisms of environmental regulationof virulence expression of enterotoxigenic Escherichia coli (ETEC). Methods Expressions of virulent factors and mRNA of virulent genes were determined by ELISA and DNA-RNA hybridization method respectively. The comparisons of expression of ETEC virulence were made between that with gyrase inhibitors (novobiocin or coumermycinA1) and that without inhibitors. Results A dose dependence relationship was found between the expressions of virulent factors and virulence mRNA. The effects of strains clones in different growth conditions also seen in the conditions treated with gyrase inhibitors. In normal growth condition with gyrase inhibitors, both of ETEC strains density and expression of virulence mildly decreased. But while change growth conditions and in the presence of novobiocin 20μg/ml or coumermycinA1 2μg/ml, expressions of virulent factors and mRNA of virulent genes increased obviously. Conclusion These results suggest that the environmental regulations of virulence of ETEC may be at the level of transcription, in witch DNA supercoilling of regulatory gene on chromosome may be involved.