[Escherichia coli O157:H7 strains carrying Shiga toxin 2 variant slt2vha were isolated from Xuzhou City of Jiangsu Province].

Objective: To monitor the changes of predominant Shiga toxin types of Escherichia coli O157:H7 in Xuzhou City, Jiangsu Province.

Methods: PCR typing with slt2-specific primer pairs (slt2cslt2, slt2v1slt2v2), hybridization of chromosome DNA digested by PstI, and DNA sequencing of PCR products. with slt2-specific primer pairs (slt2cslt2d; slt2eslt2f) were conducted on 14 strains of E. coli isolated from diarrhea patients and dung beetles in 1999 and 2000.

Results: The 5 strains of E. coli isolated from diarrhea patients in 1999 carried slt1 and slt2. The 1 strains of E. coli O157:H7 isolated from diarrhea patients and the 5 strains isolated from dung beetles in 2000 only carried slt2vha, a variance of Shiga toxin 2.

Conclusion: The predominant Shiga toxin types of E. coli O157:H7 in Xuzhou changed 1999 - 2000, which may be related to the changes of epidemiological features of E. coli O157:H7 infection in Xuzhou. A genotyping method based on restriction fragment length polymorphism (RFLP) analysis of a B-subunit-encoding DNA fragment obtained by PCR described in this study is a useful tool to identify slt2 gene and slt2 variant gene in epidemiological studies with O157:H7 strains.