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Journal of Clinical Microbiology, 10 1996, 2364-2367, Vol 34, No. 10
H Schmidt and H Karch
Thirty-six Shiga toxin-producing Escherichia coli (STEC) O111:H- strains,
18 of which were isolated from patients with hemolytic-uremic syndrome
(HUS) and 18 from patients suffering from diarrhea, were investigated for
their enterohemolytic phenotypes and genotypes. Twenty- two strains were
EHEC hemolysin (EHEC Hly) positive by probe hybridization and by PCR with
sequences complementary to the EHEC hlyA gene of E. coli O157:H7, but only
20 of these were hemolytic on blood agar plates. The remaining 14 strains
were EHEC Hly negative according to DNA-based methods and did not express
the enterohemolytic phenotype. The enterohemolytic phenotype was observed
in 16 of 18 (88%) strains from patients with HUS but only in 4 of 18
(22.2%) of the STEC O111:H- strains from patients with diarrhea. All STEC
O111:H- strains carried large plasmids, as shown by plasmid analysis, but
only plasmids of EHEC Hly probe-positive strains hybridized with the CVD419
probe. A BamHI fragment of approximately 12 kb was cloned from the large
plasmid of the E. coli O111:H- strain 78/92 and shown to mediate hemolytic
activity when transformed into the E. coli laboratory strain HB101. The
EHEC O111 hlyA gene was sequenced completely and shown to have 99.4%
sequence identity to the corresponding EHEC O157 hlyA gene of the E. coli
O157:H7 strain EDL 933. Our results indicate that detection of EHEC Hly
either by DNA-based methods or by investigation of the enterohemolytic
phenotype on blood agar alone is insufficient for screening STEC O111
strains. However, the high incidence of EHEC Hly in isolates from patients
with HUS and its rare occurrence in isolates from patients with diarrhea
may indicate that STEC O111 strains have a distinct pathogenic potential
for humans and that the presence of EHEC Hly increases the ability of an
STEC O111 strain to cause extraintestinal complications in humans.
Copyright © 1996 by the American Society for Microbiology. All rights reserved.
Enterohemolytic phenotypes and genotypes of shiga toxin-producing Escherichia coli O111 strains from patients with diarrhea and hemolytic- uremic syndrome
Institut fur Hygiene und Mikrobiologie, Universitat Wurzburg, Germany.
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