Abstract
BackgroundSalmonella is among the most significant pathogens causing food and feed safety concerns. This study examined the rapid detection of Salmonella in various types of food and feed samples by coupling loop-mediated isothermal amplification (LAMP) with a novel reporter, bioluminescent assay in real-time (BART). Performance of the LAMP-BART assay was compared to a conventional LAMP and the commercially available 3M Molecular Detection Assay (MDA) Salmonella.ResultsThe LAMP-BART assay was 100 % specific among 178 strains (151 Salmonella and 27 non-Salmonella) tested. The detection limits were 36 cells per reaction in pure culture and 104 to 106 CFU per 25 g in spiked food and feed samples without enrichment, which were comparable to those of the conventional LAMP and 3M MDA Salmonella but 5–10 min faster. Ground turkey showed a strong inhibition on 3M MDA Salmonella, requiring at least 108 CFU per 25 g for detection. The correlation between Salmonella cell numbers and LAMP-BART signals was high (R2 = 0.941–0.962), suggesting good quantification capability. After 24 h enrichment, all three assays accurately detected 1 to 3 CFU per 25 g of Salmonella among five types of food (cantaloupe, ground beef, ground turkey, shell eggs, and tomato) and three types of feed (cattle feed, chicken feed, and dry dog food) examined. However, 101 CFU per 25 g was required for cattle feed when tested by 3M MDA Salmonella.ConclusionsThe Salmonella LAMP-BART assay was rapid, specific, sensitive, quantitative, and robust. Upon further validation, it may become a valuable tool for routine screening of Salmonella in various types of food and feed samples.
Highlights
Salmonella is among the most significant pathogens causing food and feed safety concerns
We aimed to develop and optimize an inhouse Salmonella loop-mediated isothermal amplification (LAMP)-bioluminescent assay in real-time (BART) assay and to apply the assay in various types of food and feed samples
The optimized LAMP-BART assay The final LAMP-BART reaction mix in a total volume of 25 μl contained all core reagents listed in the Methods section and two (polyvinylpyrrolidone (PVP) and trehalose) out of the four facilitators evaluated
Summary
Salmonella is among the most significant pathogens causing food and feed safety concerns. This study examined the rapid detection of Salmonella in various types of food and feed samples by coupling loop-mediated isothermal amplification (LAMP) with a novel reporter, bioluminescent assay in real-time (BART). Nontyphoidal Salmonella is a zoonotic agent of significant food and feed safety concerns. To reduce Salmonella outbreaks and illnesses associated with food and feed products, a multifaceted approach from farm to table is required. Rapid, reliable, and robust detection of Salmonella in food and feed remains elusive [6]. A growing number of molecular methods, including PCR and real-time quantitative PCR (qPCR) have been developed and applied to detect Salmonella in a variety of food and feed products [8,9,10,11]. Specific, and sensitive, PCR-based nucleic acid amplification tests (NAATs) require a sophisticated thermal cycling instrument and are susceptible to inhibitors in food and feed matrices [12, 13], limiting their wider application
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