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Infection and Immunity, July 2001, p. 4447-4457, Vol. 69, No. 7
Institut für Hygiene und Mikrobiologie
der Universität Würzburg, D-97080
Würzburg,1 and Institut für
Molekulare Infektionsbiologie der Universität Würzburg,
D-97070 Würzburg,2 Germany
Received 22 December 2000/Returned for modification 7 March
2001/Accepted 9 April 2001
Sorbitol-fermenting (SF) enterohemorrhagic Escherichia
coli (EHEC) O157:H
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.7.4447-4457.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Novel Type of Fimbriae Encoded by the Large Plasmid
of Sorbitol-Fermenting Enterohemorrhagic Escherichia
coli O157:H
have emerged as important
causes of diarrheal diseases and the hemolytic-uremic syndrome in
Germany. In this study, we characterized a 32-kb fragment of the
plasmid of SF EHEC O157:H
, pSFO157, which differs
markedly from plasmid pO157 of classical non-sorbitol-fermenting EHEC
O157:H7. We found a cluster of six genes, termed sfpA,
sfpH, sfpC, sfpD,
sfpJ, and sfpG, which mediate mannose-resistant hemagglutination and the expression of fimbriae. sfp genes are similar to the pap genes,
encoding P-fimbriae of uropathogenic E. coli, but the
sfp cluster lacks homologues of genes encoding subunits
of a tip fibrillum as well as regulatory genes. The major pilin, SfpA,
despite its similarity to PapA, does not cluster together with known
PapA alleles in a phylogenetic tree but is structurally related to the
PmpA pilin of Proteus mirabilis. The putative adhesin
gene sfpG, responsible for the hemagglutination
phenotype, shows significant homology neither to papG
nor to other known sequences. Sfp fimbriae are 3 to 5 nm in diameter,
in contrast to P-fimbriae, which are 7 nm in diameter. PCR analyses
showed that the sfp gene cluster is a characteristic of
SF EHEC O157:H
strains and is not present in other EHEC
isolates, diarrheagenic E. coli, or other
Enterobacteriaceae. The sfp gene cluster
is flanked by two blocks of insertion sequences and an origin of plasmid replication, indicating that horizontal gene transfer may have
contributed to the presence of Sfp fimbriae in SF EHEC O157:H
.
*
Corresponding author. Mailing address: Institut
für Hygiene und Mikrobiologie der Universität
Würzburg, Josef-Schneider-Str. 2, D-97080 Würzburg,
Germany. Phone: 49-931-2013981. Fax: 49-931-2013445. E-mail:
wbrunder{at}hygiene.uni-wuerzburg.de.
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