[Using multiplex PCR for the detection of virulence genes in Escherichia coli O157:H7]

To detect and characterize the virulence genes in E. coli O157:H7 isolated from various reservoir in six areas of Jiangsu province.

The virulence genes of Shiga-like toxin (SLT(1) and SLT(2)), intimin (eaeA) and hemolysin (hlyA) were chosen as the target genes and amplified in multiplex PCR assays.

Of the eighty-five E. coli O157:H7 strains, the overall virulence gene prevalence was found to be 56.5% (48/85). The prevalence rates virulence genes of isolates from various areas were different from 0% up to 90.5%. It seemed to exist a relationship between the virulence gene prevalence and the level of incidence. In the areas where rates of incidence were divided into high, low, sporadic or zero, the prevalence rates were 85.7% (36/42), 52.6% (10/19) and 8.3% (2/24), respectively. The prevalence rates of isolates were also different from various reservoirs, decreasing by sheep, cattle, pig and poultry. One isolate from a rabbit was positive for SLT(2), eaeA and hly genes. Of forty-eight isolates carrying virulence genes, 38 (79.2%) had SLT(2), eaeA and hly genes, taking the dominate virulence gene pattern, 8 (16.6%) had all of the four virulence genes 2 (4.2%) had both SLT(2) and hly genes respectively. In addition, SLT(1) gene showed a lower prevalence, which was different from some findings abroad.

Since virulence gene pattern of E. coli O157:H7 is an important molecular epidemiological marker, it can provide an useful information for epidemiologic studies, and helpful to the design of prevention and control strategies. For virulence gene detection, multiplex PCR seems to be a simple, rapid, specific and sensitive method.