Method for the detection of priority Shiga toxin-producing Escherichia coli in beef trim
| Autor: | Sam Mohajer, George Huszczynski, Burton W. Blais, Martine Gauthier, Alexander Gill |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
Serotype
food.ingredient Meat Virulence Factors Colony Count Microbial Virulence Food Contamination Microbiology Polymerase Chain Reaction law.invention fluids and secretions food law STX2 Multiplex polymerase chain reaction Agar Animals Serotyping Polymerase chain reaction Intimin biology Shiga-Toxigenic Escherichia coli bacterial infections and mycoses biology.organism_classification Virology Food Microbiology Cattle Bacteria Food Science |
| Zdroj: | Journal of food protection. 76(10) |
| ISSN: | 1944-9097 |
| Popis: | A method has been developed for the detection in beef trim of priority Shiga toxin-producing E. coli (STEC) strains, defined as E. coli possessing the virulence factors stx1 and/or stx2 and intimin (eae), with O serogroups O26, O45, O103, O111, O121, O145, or O157. The method is based on recovery of the target bacteria by overnight enrichment in a broth optimized for recovery of O157 and non-O157 STEC, followed by screening using multiplex PCR techniques targeting (i) stx1, stx2, and eae (STE PCR) and (ii) gene sequences associated with the seven priority O serogroups (Poly O PCR), and then direct plating of broth samples positive in both STE and Poly O PCR onto Rainbow agar. Colonies on agar media were screened batchwise for STEC by the STE PCR, and presumptive isolates were characterized using a multiplex PCR and cloth-based hybridization array system targeting key virulence and O serogroup-specific markers. Using one representative strain of each priority O serogroup individually inoculated in beef trim samples, the method exhibited a limit of detection approaching 1 to 2 viable STEC cells per 65 g. None of the uninoculated trim samples produced positive results with either of the screening PCR procedures or on analysis of colonies recovered on plating media. STEC-negative samples were readily identified by screening PCR within 24 h, with a turnaround time of fewer than 4 days for confirmation of positives. The inclusivity and exclusivity characteristics of the screening PCR techniques were verified using a total of 65 different priority STEC strains: 24 nonpriority STEC, 15 non-STEC bacteria, and only those strains bearing the targeted characteristics produced screening PCR-positive results. |
| Databáze: | OpenAIRE |
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