P3-176 Evaluation of a Rapid Isothermal Amplification Method and Two Enrichment Protocols for Salmonella Detection in Frozen Strawberries

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Jorge Adrián Muniz Flores , Universidad de Guadalajara , Guadalajara , Mexico
Dalia Lorena Rodríguez Herrera , Universidad de Guadalajara , Guadalajara , Mexico
Julia Perez-Montano , Universidad de Guadalajara , Guadalajara , Mexico
Gustavo González-González , 3M Food Safety Mexico , Guadalajara , Mexico
Ma. Ofelia Rodríguez-García , Universidad de Guadalajara , Guadalajara , Mexico
Introduction: Fresh and refrigerated strawberries can be a pathogen vehicle; Survival of Salmonella in this product has been reported. Strawberries have low pH (3.0-3.9) and high amounts of phenolic compounds that may affect the recovery of Salmonella and inhibit molecular reactions. Sample preparation and enrichment stage are critical for Salmonelladetection. Use of technologies such 3M™ Molecular Detection Assay provides real-time detection and next day results

Purpose: To evaluate the performance of a molecular based method with a single and two enrichment step for the recovery of Salmonellafrom frozen comminuted strawberries.

Methods: A Salmonellaspp. cocktail (Typhimurium, Agona, Poona, Bardo and Saint Paul) was used to inoculate -samples of frozen comminuted strawberry by dipping. Three inoculum levels were used: high (50-100 CFU/sample), low (4-8 CFU/sample) and uninoculated level. Each 25g-sample was placed on a sterile bag and added with 225 mL of 3M™ Buffered Peptone Water-ISO and incubated 24h at 35°C (single enrichment protocol). Aliquots of 0.1 mL were transferred to 10 mL Rappaport Vassiliadis broth (RV-10) and incubated 24h at 41.5°C (two step enrichment protocol). All samples were culture confirmed according the FDA-BAM.

Results: No significant differences were found (P>0.05) when this rapid test were compared with the traditional method. Use of a single or double enrichment provides same recovery rate for Salmonella detection regardless the inoculum level (P>0.05).  One uninoculated sample was reported as positive by the rapid method and confirmed by culture. 

Significance: Use MDA assay with a single enrichment step for detection of Salmonella on frozen and comminuted strawberries provide fast and accurate results that are equivalent to the traditional method.