Presence of shiga toxin-producing Escherichia coli O157-H7 and the Stx2 gene and antibody response to shiga toxin 2 in dairy cattle in Chongqing, People Republic of China.

This study intended to acquire the data on Escherichia coli O157:H7 isolated from dairy cattle, heifers, and calves, and of Stx2 expressed in STEC in Chongqing. Three hundred cattle rectal faecal samples were collected and E. coli O157:H7 was identified by the isolation of the bacteria, serological tests, and PCR. Moreover, the stx2 gene’s genome was examined. Three hundred and twenty six milk samples were tested for the presence of immunoglobulin G antibodies to Stx2. Six E. coli O157:H7 isolates, which did not carry stx2 were obtained from the faecal samples. Forty seven positive Stx2 antibody samples were obtained in the milk samples, whereas the Stx2 antibody was not detected in the farm where the E. coli O157:H7 isolates were obtained. The prevalence of O157:H7 is lower than the prevalence of the Stx2 antibody, and the isolates lack stx2. However, it is possible that the non-O157 STEC transfers the stx2 gene to O157:H7 horizontally, and makes O157:H7 become more virulent.