针对大肠杆菌O156血清群的特异性DNA分型方法的建立

Escherichia coli O156 strains are frequently isolated from diarrheic and healthy animals and always express intimin, which is a virulence-associated factor and required for the formation of attaching-effacing (AE) lesions. The O antigen gene cluster of E. coli O156 type strain was sequenced, and 16 open reading frames were assigned functions on the basis of homology. The identity of the putative wzy gene was confirmed by comparison of LPS phenotypes between a wzy deficient mutant and the wild type of E.coli O156. By screening against 186 E. coli and Shigella type strains, two genes specific for E. coli O156 were identified. A PCR assay based on the specific genes were developed and tested on 10 clinical and environmental isolates of O156 and 20 isolates of other serogroups in a double-blind test. The sensitivity of the PCR assay was also determined, and as little as 1.92 pg per μl of chromosomal DNA and as few as 0.1 CFU per g of contaminated beef and water samples can be detected. The PCR assay developed in this study can be used for detection and identification of E.coli O156 strains from environmental samples rapidly and accurately, and it is especially useful when dealing with large number of samples.