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Infect Immun, May 1998, p. 2040-2051, Vol. 66, No. 5
Center for Vaccine
Development1 and
Department of
Comparative Medicine and Pathology,3 University
of Maryland School of Medicine, Baltimore, Maryland 21201;
International Center for Diarrheal Disease Research, Dhaka,
Bangladesh4; and
Department of
Microbiology,
Received 5 September 1997/Returned for modification 23 October
1997/Accepted 29 January 1998
Escherichia coli strains producing alpha-hemolysin have
been associated with diarrhea in several studies, but it has not been clearly demonstrated that these strains are enteropathogens or that
alpha-hemolysin is an enteric virulence factor. Such strains are
generally regarded as avirulent commensals. We examined a collection of
diarrhea-associated hemolytic E. coli (DHEC) strains for
virulence factors. No strain produced classic enterotoxins, but they
all produced an alpha-hemolysin that was indistinguishable from that of
uropathogenic E. coli strains. DHEC strains also produced
other toxins including cytotoxic necrotizing factor 1 (CNF1) and novel
toxins, including a cell-detaching cytotoxin and a toxin that causes
HeLa cell elongation. DHEC strains were enteropathogenic in the RITARD
(reversible intestinal tie adult rabbit diarrhea) model of diarrhea,
causing characteristic enteropathies, including inflammation, necrosis,
and colonic cell hyperplasia in both small and large intestines.
Alpha-hemolysin appeared to be a major virulence factor in this model
since it conferred virulence to nonpathogenic E. coli
strains. Other virulence factors also appear to be contributing to
virulence. These findings support the epidemiologic link to diarrhea
and suggest that further research into the role of DHEC and
alpha-hemolysin in enteric disease is warranted.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Characterization of the Roles of Hemolysin and Other Toxins
in Enteropathy Caused by Alpha-Hemolytic Escherichia
coli Linked to Human Diarrhea
*
Corresponding author. Mailing address: Center for
Vaccine Development, University of Maryland School of Medicine, 685 W
Baltimore St., Baltimore, MD 21201. Phone: (410) 706 2493. Fax: (410)
706 6205. E-mail: selliott{at}umaryland.edu.
Infect Immun, May 1998, p. 2040-2051, Vol. 66, No. 5
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
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