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Journal of Clinical Microbiology, February 2007, p. 333-339, Vol. 45, No. 2
0095-1137/07/$08.00+0 doi:10.1128/JCM.01627-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.
National Reference Laboratory for Escherichia coli, Centre for Infectiology and Pathogen Characterization,1 Department of Biological Safety, Federal Institute for Risk Assessment, D-12277 Berlin, Germany2
Received 7 August 2006/ Returned for modification 1 November 2006/ Accepted 7 November 2006
Flagellar type H8 is associated with many strains of pathogenic Shiga toxin-producing Escherichia coli (STEC), such as O8, O22, O111, O174, and O179 strains. Serological typing of the H8 antigen is limited to motile strains only and suffers from cross-reactivity between flagellar H8 and H40 antigens. In order to develop a method useful for typing of motile and nonmotile STEC O111 and other strains, we have analyzed the flagellar antigen (fliC) genes in representative E. coli H8 and H40 types. Two genotypes of the fliC gene encoding H8 (the fliC-H8 gene) were identified. Genotype fliC-H8a was found to be conserved in STEC O111, O174, and O179 strains; and type fliC-H8b was associated with STEC O8 and O22 strains. Sequence variations were also found in the genetically closely related fliC-H40 gene, although the latter was not found to be associated with STEC strains. A PCR was developed for the specific identification of the fliC-H8 and the fliC-H40 genes in motile and nonmotile E. coli strains. Digestion of PCR products with HhaI resulted in restriction fragment length polymorphisms (RFLPs) which were associated with genotypes fliC-H8a and -H8b as well as with genotypes fliC-H40a and -H40b. The fliC-specific PCR/RFLP typing method was suitable for the rapid typing of motile and nonmotile STEC O8, O22, O111, O174, and O179 strains from different sources whose fliC-H8 genotypes were found to be highly conserved. The fliC genotyping method is advantageous over serotyping and is useful for epidemiological investigations and studies of the evolution of STEC clones.
Published ahead of print on 29 November 2006.
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