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Journal of Clinical Microbiology, June 1998, p. 1604-1607, Vol. 36, No. 6
Institut für Hygiene und
Infektionskrankheiten der Tiere,
Received 22 September 1997/Returned for modification 20 January
1998/Accepted 13 March 1998
Shiga toxin-producing Escherichia coli (STEC) strains
of serogroup O118 are the most prevalent group among STEC strains in diarrheic calves in Germany (L. H. Wieler, Ph.D. thesis,
University of Giessen, 1997). To define their virulence properties, 42 O118 (O118:H16 [n = 38] and O118:H
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Virulence Properties of Shiga Toxin-Producing Escherichia
coli (STEC) Strains of Serogroup O118, a Major Group of STEC
Pathogens in Calves
[n = 4]) strains were characterized. The
strains displayed three different Stx combinations (Stx1 [36 of 42],
Stx1 and Stx2 [2 of 42], and Stx2 [4 of 42]). A total of 41 strains
(97.6%) harbored a large virulence-associated plasmid containing
hlyEHEC (hly from enterohemorrhagic
E. coli). The strains' adhesive properties varied in
relation to the eukaryotic cells tested. Only 28 of 42 strains (66.7%)
showed localized adhesion (LA) in the human HEp-2 cell line. In
contrast, in bovine fetal calf lung (FCL) cells, the number of
LA-positive strains was much higher (37 of 42 [88.1%]). The locus of
enterocyte effacement (LEE) was detected in 41 strains (97.6%).
However, not all LEE-positive strains reacted positively in the
fluorescence actin-staining (FAS) test, which indicated the attaching
and effacing (AE) lesion. In HEp-2 cells, only 22 strains (52.4%) were
FAS positive, while in FCL cells, the number of FAS-positive strains
was significantly higher (38 of 42 [90.5%; P < 0.001]). In conclusion, the vast majority of the O118 STEC strains
from calves (41 of 42 [97.6%]) have a high virulence potential
(stx, hlyEHEC, and LEE). This virulence potential and the high prevalence of STEC O118 strains in
calves suggest that these strains could be a major health threat for
humans in the future. In addition, the poor association between results
of the geno- and phenotypical tests to screen for the AE ability of
STEC strains calls the diagnostic value of the FAS test into question.
*
Corresponding author. Mailing address: Institut
für Hygiene und Infektionskrankheiten der Tiere,
Justus-Liebig-Universität Giessen, Frankfurter Str. 89, D-35392 Giessen, Germany. Phone: 49 641 9938303. Fax: 49 641 9938309. E-mail:
lothar.h.wieler{at}vetmed.uni-giessen.de.
Journal of Clinical Microbiology, June 1998, p. 1604-1607, Vol. 36, No. 6
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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