Objective: To understand the epidemiological characteristics of enterohaemorrhagic Escherichia coli (EHEC) O157 and to determine the degree of its genetic relations.
Methods: Polymerase chain reaction (PCR) techniques and chromosomal DNA digested by restriction enzyme Xba I according to PulseNet directions by pulsed field gel electrophoresis (PFGE) method were applied to 300 E. coli O157 strains isolated from patients and animal sources from 1988 to 2005 from Henan, Jiangsu and Anhui provinces.
Results: Very high prevalence of stx2 gene in EHEC O157:H7 strains isolated from some provinces of China was found and variation existed in some strains. We got 161 PFGE patterns from 300 strains. The stx2-producing strains could be clearly separated from stx2 variation-producing strains.
Conclusion: The variability of restriction enzyme-digestion patterns of O157 genomes suggested that the presence of some genomic diversity among the strains did exist.