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2021 FDA Science Forum

Platform and Reagent Extensions of a Salmonella Loop-Mediated Isothermal Amplification (LAMP) Method in Animal Food

Authors:
Poster Author(s)
Domesle, Kelly J., FDA/CVM; Young, Shenia R., FDA/CVM; Ge, Beilei, FDA/CVM
Center:
Contributing Office
Center for Veterinary Medicine

Abstract

Poster Abstract

The Salmonella LAMP method was recently added to the FDA’s Bacteriological Analytical Manual (BAM) to screen animal food for Salmonella contamination and to confirm presumptive Salmonella isolated from any food source. In this study, we extended the Salmonella LAMP method to two platforms (Genie II and AB 7500 Fast) and three master mixes (ISO-001, ISO-004, and NEB WarmStart) for a total of six platform-master mix combinations. Sensitivity was evaluated with a serially diluted Salmonella Typhimurium LT2 culture, inclusivity with 100 different Salmonella serovars, and exclusivity with 30 non-Salmonella strains. Seven animal food matrices were evaluated including dry cat food, dry dog food, cattle feed, dairy feed, horse feed, poultry feed, and swine feed. All six platform-master mix combinations showed comparable sensitivity, consistently detecting down to the 1 cell/reaction level, except for AB 7500 Fast-NEB WarmStart kit which was 10-fold less sensitive. All six combinations were comparable in inclusivity and exclusivity. In animal food matrices, all six combinations had comparable performance in probability of detection among fractional samples as compared to the FDA’s BAM reference culture method for Salmonella. There was no difference between the Genie II and the AB 7500 FAST platforms, which is available in almost all FDA field regulatory laboratories. Regardless of platform, master mix ISO-004 was the fastest, frequently detecting positives within 5 min of the real-time assay starting. In conclusion, LAMP was demonstrated to be a versatile and robust molecular method, highly amenable to different laboratory workflows. This improvement in Salmonella testing methods will greatly enhance the efficiency of FDA’s human and animal food testing programs for FSMA compliance, ensuring the safety of these FDA-regulated products.

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