A Loop-Mediated Isothermal Amplification-Based Method for Analysing Animal Feed for the Presence of Salmonella

A loop-mediated isothermal amplification (LAMP)-based method has been developed for the analysis of animal feed for the presence of Salmonella spp. The method is compatible with the standard culture-based method ISO 6579:2002. Samples comprising 100 g feed are pre-enriched in 900 ml buffered peptone water, and then 2× 100-μl aliquots are taken, one for secondary enrichment in a LAMP-friendly broth and the other for secondary enrichment according to ISO 6579:2002. A 3-μl aliquot of the LAMP-friendly culture is added directly into a LAMP reaction. LAMP-positive signals are considered presumptive of the presence of Salmonella spp.; confirmation is obtained by continuation of ISO 6579:2002. Negative LAMP reactions can be considered as signifying that the sample does not contain viable Salmonella. The LAMP assay incorporates an internal amplification control (IAC); the target and IAC signals are distinguished by the difference in annealing temperatures of the amplicons. The method provides simple and reliable screening of feedstuffs for Salmonella spp., with uncontaminated samples being identified in 24 h less than using the current ISO standard method alone. The method was used to analyse 79 samples of animal feed and identified 13 Salmonella-positive samples.