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. 1999 Nov;37(11):3491-6.
doi: 10.1128/JCM.37.11.3491-3496.1999.

Escherichia coli O157:H7 and O157:H(-) strains that do not produce Shiga toxin: phenotypic and genetic characterization of isolates associated with diarrhea and hemolytic-uremic syndrome

H Schmidt  1 , J Scheef, H I Huppertz, M Frosch, H Karch
Affiliations

Escherichia coli O157:H7 and O157:H(-) strains that do not produce Shiga toxin: phenotypic and genetic characterization of isolates associated with diarrhea and hemolytic-uremic syndrome

H Schmidt et al. J Clin Microbiol. 1999 Nov.

Abstract

We have isolated one sorbitol-nonfermenting (SNF) Escherichia coli O157:H7 isolate and five sorbitol-fermenting (SF) E. coli O157:H(-) isolates that do not contain Shiga toxin (Stx) genes (stx). Isolates originated from patients with diarrhea (n = 4) and hemolytic-uremic syndrome (HUS) (n = 2). All isolates harbored a chromosomal eae gene encoding gamma-intimin as well as the plasmid genes E-hly and etp. The E. coli O157:H7 isolate was katP and espP positive. Respective sera obtained from the patient with HUS contained antibodies to the O157 lipopolysaccharide antigen. The stx-negative E. coli O157:H7 isolate is genetically related to stx-positive SNF E. coli O157:H7. All stx-negative SF E. coli O157:H(-) isolates belong to the same genetic cluster and are closely related to stx-positive SF E. coli O157:H(-) isolates. Our data indicate that stx-negative E. coli O157:H7/H(-) variants may occur at a low frequency and cannot be recognized by diagnostic methods that target Stx.

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Figures

FIG. 1
FIG. 1
Agarose gel electrophoresis of fliC PCR products of E. coli O157 strains restricted with RsaI. Lanes M, molecular size marker (1-kb ladder; Gibco GmbH); lane 1, E. coli O157:H7 EDL933; lane 2, E. coli O157:H7 19685; lane 3, SF E. coli O157:H− 702/88; lane 4, SF E. coli O157:H− 1533/97; lane 5, SNF E. coli O157:H− 3817/96; lane 6, SNF E. coli O157:H− E32511; lane 7, SF E. coli O157:H− 2937; lane 8, SF E. coli O157:H− 6790; lane 9, SF E. coli O157:H− 431; lane 10, SF E. coli O157:H− 659; lane 11, SF E. coli O157:H− 2576; lane 12, E. coli O157:H19 693/91; lane 13, E. coli O157:H43 241/88; lane 14, E. coli O157:H45 1083/87; and lane 15, E. coli O157:H45 904/90.
FIG. 2
FIG. 2
Southern blot hybridization of EcoRI-restricted chromosomal DNAs of control strains E. coli O157:H7 EDL933 (lanes 1) and E. coli O157:H− E32511 (lanes 2) and the O157 isolates 19685 (lanes 3), 2937 (lanes 4), 6790 (lanes 5), 431 (lanes 6), 659 (lanes 7), and 2576 (lanes 8) with probes specific for eae (A), stx1 (B), and stx2 (C) under low-stringency conditions. M, molecular size marker.
FIG. 3
FIG. 3
Dendrogram of E. coli O157 strains used in this study based on RAPD analysis-PCR pattern similarity. The percentages represent band pattern similarities as calculated with the Jacquard algorithm.
See this image and copyright information in PMC

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