title: Improved method for the routine identification of toxigenic Escherichia coli by DNA amplification of a conserved region of the heat-labile toxin A subunit.
abstract: This report describes a DNA amplification procedure for routine identification of heat-labile-toxin-producing Escherichia coli. Two oligonucleotide primers were used in a polymerase chain reaction procedure to amplify a highly conserved region of the A subunit of the heat-labile enterotoxin gene. Amplifications were done directly on E. coli colonies from plates when Salmonella, Shigella, or parasite infections were excluded as agents of the severe diarrhea in the patients. The conditions for the polymerase chain reaction method were empirically determined, and the procedure is inexpensive, sensitive, and specific. Positive results can be obtained over a wide variation in bacterial numbers, with no inhibition of Thermus aquaticus DNA polymerase. Detection of the amplified product can be done by agarose gel electrophoresis, which is specific and sensitive enough for routine diagnosis of this pathogen in clinical isolates. If greater sensitivity and specificity are required, hybridization with 32P- or alkaline phosphatase-labeled oligonucleotide probes can be used. Our results suggest that heat-labile-toxin-producing E. coli is responsible for about 9% of nondiagnosed diarrhea cases in Tygerberg Hospital, Tygerberg, Republic of South Africa.
authors.affiliation: Department of Medical Physiology and Biochemistry, University of Stellenbosch Medical School, Tygerberg, Republic of South Africa.
authors.forename: T
authors.initials: T
authors.lastname: Victor
authors.forename: R
authors.initials: R
authors.lastname: du Toit
authors.forename: J
authors.initials: J
authors.lastname: van Zyl
authors.forename: A J
authors.initials: AJ
authors.lastname: Bester
authors.forename: P D
authors.initials: PD
authors.lastname: van Helden
mesh_terms: D000469:Alkaline Phosphatase; D001427:Bacterial Toxins / Q000235:genetics*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000032:analysis*; D003967:Diarrhea / Q000175:diagnosis; D004587:Electrophoresis, Agar Gel; D004768:Enterotoxins / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics* / Q000472:pathogenicity; D004927:Escherichia coli Infections / Q000175:diagnosis*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D006801:Humans; D007223:Infant; D008969:Molecular Sequence Data; D010761:Phosphorus Radioisotopes; D016133:Polymerase Chain Reaction; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D001427:Bacterial Toxins; D004269:DNA, Bacterial; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D010761:Phosphorus Radioisotopes; C027538:heat-labile enterotoxin, E coli; D000469:Alkaline Phosphatase