Sequence diversity of the Escherichia coli H7 fliC genes: implication for a DNA-based typing scheme for E. coli...

Flagellar (H) antigens are mostly encoded by genes at the fliC locus in E. coli. We have sequenced 11 H7 fliC genes from Escherichia coli strains that belong to seven O serotypes. These sequences, together with those of nine other H7 fliC genes (from strains of three different O serotypes) sequenced recently (S. D. Reid, R. K. Selander, and T. S. Whittam, J. Bacteriol. 181:153-160, 1999), include 10 different sequences. The differences between these 10 sequences range from 0.06 to 3.12%. By comparison with other E. coli flagellin genes, we have identified primer length sequences specific for H7 genes in general and others specific for H7 genes of O157 and O55 strains: the specificity was confirmed by PCR testing the type strains for all 53 E. coli H types. We have previously identified genes specific for the E. coli O157 antigen, and use of the combination of O157- and H7-specific primers allows the sensitive and rapid detection of O157:H7 E. coli strains, which cause the majority of hemorrhagic colitis cases.