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Journal of Clinical Microbiology, Mar 1995, 519-524, Vol 33, No. 3
K Ramotar, B Waldhart, D Church, R Szumski and TJ Louie
A method for the rapid detection of verotoxin-producing Escherichia coli in
stool samples by PCR was evaluated. Verotoxin-1 and verotoxin-2 genes in
DNA extracted directly from stool samples were amplified with
oligonucleotide primers. Stools spiked with control organisms, E. coli C600
(H19B) (verotoxin-1) or E. coli C600 (933W) (verotoxin-2), demonstrated
that verotoxin-1-containing organisms could be detected at 10(2) CFU per
0.1 g of stool and verotoxin-2-containing organisms could be detected at
10(7) CFU per 0.1 g of stool. Testing of stool samples from patients with
diarrhea showed a high concordance between PCR positivity and the presence
of verotoxin-producing E. coli, determined by isolation of serotype O157:H7
on sorbitol-MacConkey medium (34 of 35 stool samples) or by colony blots
with gene probes (19 of 21 stool samples). Conversely, only 1 of 20 (5.0%)
stool samples that were O157:H7 culture negative and colony blot negative
and that contained free verotoxin only was positive by PCR. As well, only 4
of 145 (2.8%) stool samples that were negative for serotype O157:H7 or free
verotoxin were PCR positive. PCR of DNA extracted directly from stool
samples provides a rapid method for the detection of stool samples
containing verotoxin-producing E. coli compared with colony blot testing.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Direct detection of verotoxin-producing Escherichia coli in stool samples by PCR
Division of Infectious Diseases, Calgary General Hospital, Alberta, Canada.
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