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以一对合成的特异性寡核苷酸片段为引物，通过聚合酶链式反应（ＰＣＲ），对不同血清型的ＥＴＥＣ以及１０４份牛、猪及鸡源大肠杆菌分离物中ＬＴ基因片段进行扩增。３株已知血清型ＥＴＥＣ、１３份牛源、６份鸡源、１０份猪源的大肠杆菌扩增后可见一条３１４ｂｐ的片段，而非ＥＴＥＣ大肠杆菌、沙门氏菌等扩增后未出现这一片段。扩增产物用ＳｍａＩ酶解为１９０ｂｐ和１２４ｂｐ两个片段。印迹杂交表明，３１４ｂｐ扩增片段及ＳｍａＩ酶解的１２４ｂｐ和１９０ｂｐ片段均能与特异的ＬＴＢ基因探针杂交，Ｄｏｔ－印迹杂交与ＰＣＲ对样品的扩增结果相一致。
Using a pair of synthetic specific oligonucleotide fragments as primers, the LT gene fragments of ETECs with different serotypes and 104 isolates of bovine, porcine and chicken origin were amplified by polymerase chain reaction (PCR) increase. A total of 314bp fragments of 3 Escherichia coli strains of known ETECs, 13 bovine cows, 6 chicken breeders and 10 pig breeders were obtained. However, no such fragment appeared after amplification of ETEC, Salmonella and so on . The amplified product was digested with SmaI into two fragments of 190 bp and 124 bp. Blotting indicated that both the 314bp fragment and the 124bp and 190bp fragments digested by SmaI were able to hybridize with the specific LTB gene probe. The Dot-blot hybridization was consistent with the PCR amplification.