New molecular methods to detect pathogenic STEC in dairy products - Anses - Agence nationale de sécurité sanitaire de l’alimentation, de l’environnement et du travail Accéder directement au contenu
Poster De Conférence Année : 2023

New molecular methods to detect pathogenic STEC in dairy products

Résumé

E. coli strains simultaneously possessing the stx and eae genes have a high risk of causing STEC infections with HUS and diarrhea. Both virulence factors are thus targeted by detection methods of non-O157 STEC in foods (ISO13136 and MLG5B for example) in a first screening step. These detection methods generate many presumptive positives, which must then be confirmed by isolation and then phenotypic and genotypic characterization of the isolated strain to confirm the presence of all virulence factors in a single strain. This represents major financial and logistical challenges for food manufacturers. It is therefore important to improve the detection methods with the aim to increase the percentage of batches released at the end of the first screening step and to reduce the number of confirmations on isolated colonies while maintaining a high (or even higher) level of product safety. We previously identified four genetic markers (espK, espV, Z2088, and ureD), which are preferentially associated with typical EHEC (E. coli strains positive for the stx and eae genes, irrespective of their serotype), and demonstrated that they could reduce at the first screening step, the number of presumptive positive samples in beef enrichments by 48.88%. The objective of this project was to assess the contribution of these genetic markers in the dairy sector in the reduction in the number of presumptive positive samples after the first phase of screening. The high-throughput qPCR analysis of more than 4000 samples of selected DNA extracts issued from routine testing of raw milk and raw milk products demonstrated that addition of these new markers to the first screening step resulted in a systematic reduction of the number of presumptive positive samples. This reduction is more important (26% to 52%, depending on the milking animal species) in the absence of prior IMS treatment of the enrichment broth for the Top5 EHEC serotypes. However, even with prior treatment of the enrichment broths by IMS, the reduction rate varied between 5% and> 25%.

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Bactériologie
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anses-04206789 , version 1 (14-09-2023)

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  • HAL Id : anses-04206789 , version 1

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Sabine Delannoy, Mai-Lan Tran, Patrick Fach. New molecular methods to detect pathogenic STEC in dairy products. VTEC 2023 - 11th International Symposium on Shiga Toxin (Verocytotoxin) Producing Escherichia coli Infections, May 2023, Banff, Canada. ⟨anses-04206789⟩

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