title: Evaluation of detection methods for non-O157 Shiga toxin-producing Escherichia coli from food.
abstract: Shiga toxin-producing Escherichia coli (STEC) remains a major foodborne pathogen of concern across the globe. Rapid detection and isolation of this pathogen is of great importance for public health reasons. In this study the detection and isolation of four non-O157 STEC strains (O26, O103, O111, O145) from different artificially contaminated matrices, namely ground (minced) beef, cattle carcass swab, lettuce mix and sprouted soy beans, were evaluated. Low amounts of STEC were used (0.25-1.40 cfu/g) to spike the samples. All samples were enriched in parallel in Buffered Peptone Water (BPW) and Brila broth. After enrichment, detection was performed using real-time PCR (qPCR), and isolation using two chromogenic agar media, CHROMagar™ STEC and ChromID™ EHEC. Inoculation on the agar media was performed either directly after enrichment or after the use of an acid treatment procedure. Furthermore, the use of this procedure was also tested on naturally contaminated food products, using 150 stx-positive samples. Although the qPCR Cycle Threshold (Ct) values were lower after enrichment in Brila broth, no significant differences in recovery were observed between both enrichment broths. Both agar media were equally suitable for the isolation of STEC, although a significantly higher recovery was obtained when using both agar media in parallel. For samples with a Ct value above 25, an acid treatment step prior to isolation ensured a significant improvement in the recovery of STEC due to the reduction in background microbiota. This acid treatment procedure proved especially useful for the isolation of STEC from sprouted soy bean samples.
authors.affiliation: Institute for Agriculture and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium; Ghent University, Faculty of Veterinary Medicine, Department of Veterinary Public Health and Food Safety, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Bavo
authors.initials: B
authors.lastname: Verhaegen
authors.affiliation: Ghent University, Faculty of Veterinary Medicine, Department of Veterinary Public Health and Food Safety, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Inge
authors.initials: I
authors.lastname: Van Damme
authors.affiliation: Institute for Agriculture and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium; Ghent University, Faculty of Veterinary Medicine, Department of Pathology, Bacteriology and Poultry Diseases, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: Heyndrickx
authors.affiliation: Foodborne Pathogens, Scientific Institute of Public Health, Juliettte Wytsmanstraat 14, 1050 Brussels, Belgium.
authors.forename: Nadine
authors.initials: N
authors.lastname: Botteldoorn
authors.affiliation: Department of Bacteriology, Mycology and Immunology, Faculty of Veterinary Medicine, Mansoura University, Mansoura 35516, Egypt.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Elhadidy
authors.affiliation: Institute for Agriculture and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium.
authors.forename: Karen
authors.initials: K
authors.lastname: Verstraete
authors.affiliation: Foodborne Pathogens, Scientific Institute of Public Health, Juliettte Wytsmanstraat 14, 1050 Brussels, Belgium.
authors.forename: Katelijne
authors.initials: K
authors.lastname: Dierick
authors.affiliation: Foodborne Pathogens, Scientific Institute of Public Health, Juliettte Wytsmanstraat 14, 1050 Brussels, Belgium.
authors.forename: Sarah
authors.initials: S
authors.lastname: Denayer
authors.affiliation: Ghent University, Faculty of Veterinary Medicine, Department of Veterinary Public Health and Food Safety, Salisburylaan 133, 9820 Merelbeke, Belgium.
authors.forename: Lieven
authors.initials: L
authors.lastname: De Zutter
authors.affiliation: Institute for Agriculture and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium. Electronic address: Koen.DeReu@ilvo.vlaanderen.be.
authors.forename: Koen
authors.initials: K
authors.lastname: De Reu
mesh_terms: D000818:Animals; D002417:Cattle; D005506:Food Contamination / Q000032:analysis*; D005516:Food Microbiology / Q000379:methods*; D006801:Humans; D018545:Lactuca / Q000382:microbiology*; D008460:Meat / Q000382:microbiology*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D054323:Shiga-Toxigenic Escherichia coli / Q000302:isolation & purification*; D013025:Glycine max / Q000382:microbiology*
keywords: Acid treatment procedure; Detection; Food; Isolation; Shiga toxin-producing Escherichia coli (STEC)