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P2-47 A Loop-mediated Isothermal Amplification Assay for the Rapid Detection of Salmonella in Animal Feed and Pet Food

Monday, July 27, 2015
Exhibit Hall (Oregon Convention Center)
Kelly Domesle , U. S. Food and Drug Administration , Laurel , MD
Qianru Yang , Louisiana State University , Baton Rouge , LA
Beilei Ge , Food and Drug Administration , Laurel , MD
Introduction: Salmonella is a significant contaminant in animal feed and pet food. Recent outbreaks and an updated FDA guidance underscore the need for rapid and reliable detection methods in these diverse commodities. Loop-mediated isothermal amplification (LAMP) is a promising molecular method that gained wide application in food testing recently and could be applied in detecting Salmonella in animal feed and pet food.

Purpose: A modified LAMP assay was developed and evaluated for the rapid detection of Salmonella in various animal feed and pet food matrices. 

Methods: A previously published Salmonella LAMP assay was used with slightly modified primers. The assay specificity and sensitivity was determined using 186 bacterial strains (151 Salmonella and 35 non-Salmonella) and serially diluted Salmonella reference strains, respectively. Cattle feed, chicken feed, swine feed, dry cat food, and dry dog food were inoculated with serially diluted cultures (108 to 100 CFU per 25 g feed) of Salmonella serovars Newport, Enteritidis, Choleraesuis, Typhimurium, and Infantis, respectively, and tested directly or after overnight cultural enrichment. A well-established qPCR assay was run as a comparison.

Results: The Salmonella LAMP assay was 100% specific among the 186 strains tested, without false positive or false negative results. The detection limits were ca. 3.6 cells per reaction in pure culture and 105 CFU per 25 g in spiked feed samples when tested directly. After overnight enrichment, all feed samples tested positive by LAMP at 100 CFU per test portion except for cattle feed, which was positive at 101 CFU. Comparable results were obtained with qPCR.

Significance: Animal feed and pet food contaminated with Salmonella is a growing public health concern. The Salmonella LAMP assay represents a rapid, specific, sensitive, and robust alternative to qPCR for routine screening of Salmonella in these commodities.

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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