title: Assessment of commercial chromogenic solid media for the detection of non-O157 Shiga toxin-producing Escherichia coli (STEC).
abstract: Detection of Shiga toxin-producing Escherichia coli (STEC) has evolved significantly since the introduction of sorbitol-MacConkey agar. This study compares four chromogenic media (CHROMagar™ STEC, Rainbow® O157 agar, CHROMagar™ O157, and Colorex® O157) in their identification of non-O157 STEC. When 161 non-O157 STEC were directly inoculated onto each medium, detection rates on CHROMagar™ STEC, Rainbow® O157 agar, CHROMagar™ O157 and Colorex® O157 were 90%, 70%, 3.7% and 6.8%, respectively. Tellurite minimal inhibitory concentrations (MICs) correlated with growth on CHROMagar™ STEC as 20 of 22 isolates with poor or no growth had MICs ≤1μg/mL. Stool spiking experiments revealed that CHROMagar™ STEC had the highest recovery of the six most common non-O157 STEC, ranging from 30% (in mucoid stool) to 98% (in watery stool). When using clinical stool samples, CHROMagar™ STEC had a sensitivity, specificity, positive predictive value, and negative predictive value of 84.6%, 87%, 13.9%, and 99.6%, respectively.
authors.affiliation: Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB, Canada.
authors.forename: Nathan
authors.initials: N
authors.lastname: Zelyas
authors.affiliation: Alberta Provincial Laboratory for Public Health, Edmonton, AB, Canada.
authors.forename: Alan
authors.initials: A
authors.lastname: Poon
authors.affiliation: Alberta Provincial Laboratory for Public Health, Edmonton, AB, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: Patterson-Fortin
authors.affiliation: Public Health Agency of Canada, National Microbiology Laboratory@Guelph, Guelph, ON, Canada.
authors.forename: Roger P
authors.initials: RP
authors.lastname: Johnson
authors.affiliation: Alberta Provincial Laboratory for Public Health, Edmonton, AB, Canada.
authors.forename: Winki
authors.initials: W
authors.lastname: Lee
authors.affiliation: Alberta Provincial Laboratory for Public Health, Edmonton, AB, Canada; Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB, Canada. Electronic address: Linda.Chui@albertahealthservices.ca.
authors.forename: Linda
authors.initials: L
authors.lastname: Chui
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism; D001431:Bacteriological Techniques / Q000379:methods*; D002863:Chromogenic Compounds / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry*; D004927:Escherichia coli Infections / Q000175:diagnosis* / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification*; D013691:Tellurium / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D002863:Chromogenic Compounds; D003470:Culture Media; C026660:tellurous acid; D013691:Tellurium
keywords: CHROMagar™ STEC; Real-time PCR; Shiga toxin-producing Escherichia coli