腸毒素型大腸桿菌(ETEC)為引起人畜下痢疾病之主要病原菌，其產生的腸毒素，可分為熱不穩定性腸毒素(LT)及熱穩定性腸毒素的T)，由於上述引起致病因子之基因，均位於質體上，本研究乃首先探討ETEC質體DNA之分離方法，並以0.7% agarose膠體進行電泳分析，結果發現大部分ETEC之質體DNA，分佈在2kb到22 kb之間，以此質體DNA做為目標DNA，並以本研究室發展之STI基因檢測用聚合酶鏈反應(PCR)引子，進行PCR反應結果發現，所有受測STI型腸毒素大腸桿菌，皆可產生一分子量203bp之預期產物，由於此質體DNA分離方法，簡單快述，應可用於大腸桿菌其他腸毒素基因之檢測。

Enterotoxigenic Escherichia coli (ETEC) is one of the food pathogens which may cause diarrhea in humans. The enterotoxins produced by ETEC are heat labile toxins (LT) and heat stable toxins (ST). These pathogenic factors are usually encoded on the plasmid DNA of E. coli cells. In this study, E. coli plasmid DNA was isolated and subjected to 0.7% agarose gel electrophoretic analysis and the STI gene was detected by polymerase chain reaction (PCR) using new primers. It was found that most of the plasmids from ETEC cells showed molecular weights in the range of 2-22 kb and the PCR primers used specifically amplified a 203 bp fragment.