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P2-08 Detection of Salmonella from Cloves by a Modified Culture Method and Three PCR Methods

Monday, July 27, 2015
Exhibit Hall (Oregon Convention Center)
Aparna Tatavarthy , U.S. Food and Drug Administration , College Park , MD
Vikas Gill , U.S. Food and Drug Administration , College Park , MD
Laila Ali , U.S. Food and Drug Administration-CFSAN , College Park , MD
Thomas Hammack , U.S. Food and Drug Administration , College Park , MD
Guodong Zhang , U.S. Food and Drug Administration , College Park , MD
Introduction: Spices are typically added to Ready-to-Eat foods and present a unique challenge to food safety. Many spices, including cloves, have antimicrobial properties and current methods for detection of Salmonella from these food ingredients are not as sensitive as they are for foods that do not contain inhibitors.

Purpose: To improve the Bacteriological Analytical Manual (BAM) for detection of Salmonella from cloves by modifying the culture assay and integrating it with real-time PCR platforms.

Methods: A modified culture method was compared with the reference BAM method. For the modified method, 25 g of cloves were rinsed in 225 ml of tryptic-soy-broth for 60 s and the rinsate was pre-enriched. The BAM was followed for the remainder of the assay. Six trials with two clove cultivars and three Salmonella serotypes were conducted. Each trial was comprised of 40 dry-inoculated samples (10 - 810 CFU/g); 20 samples were processed by BAM method and 20 by the modified method. Pre-enrichment cultures from the modified method were used for comparison of the effectiveness of FDA-PCR, ABI-MicroSEQ® and GeneDisc® for the detection of Salmonella, with three DNA different extraction methods.

Results: With the modified method, for the six trials 100%, 30%, 100%, 90%, 95% and 80% of the 20 samples were positive for Salmonella. With the BAM method in the same trials, 75%, 0% 30%, 10%, 15%, and 25% of the samples were positive; respectively.  There was 100% correlation among all the DNA extraction methods for the various PCR platforms examined. The molecular data matched the cultural data. In conclusion, the modified culture method was more sensitive than the BAM method for the detection of Salmonella in cloves. All three PCR methods were equally effective for detection of Salmonella from cloves.

Significance: This modified culture method will substantially improve the detection of Salmonella from cloves and can potentially be applied to other spices in the future.

Back to: Poster Session 2 – Laboratory and Detection Methods; Meat, Poultry and Eggs; Dairy and Beverages; Food Law and Regulation; General Microbiology; Modeling and Risk Assessment
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