title: Direct detection of verotoxin-producing Escherichia coli in stool samples by PCR.
abstract: 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.
authors.affiliation: Division of Infectious Diseases, Calgary General Hospital, Alberta, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Ramotar
authors.forename: B
authors.initials: B
authors.lastname: Waldhart
authors.forename: D
authors.initials: D
authors.lastname: Church
authors.forename: R
authors.initials: R
authors.lastname: Szumski
authors.forename: T J
authors.initials: TJ
authors.lastname: Louie
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000032:analysis*; D001483:Base Sequence; D003967:Diarrhea / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D005243:Feces / Q000382:microbiology*; D006801:Humans; D015336:Molecular Probe Techniques; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D022622:Shiga Toxin 1
chemical_list: D001427:Bacterial Toxins; D022622:Shiga Toxin 1