A rapid, sensitive, specific and visual detection of Salmonella in retail meats using the loop-mediated isothermal amplification (LAMP), targeting the invA gene.

Salmonella is one of the major pathogenic bacteria causing food-borne diseases. The rapid detection of Salmonella in food is of great significance to food safety. In this study, the loop-mediated isothermal amplification (LAMP) method was developed and the primers were designed targeting the invA gene of Salmonella. Then, the standard samples of recombinant invA-plasmid and 100 retail meat samples were tested by LAMP and compared with the results tested by the conventional PCR and the routine China National Food Safety Standard Methods for Food Microbiological Examination-Salmonella (GB/T4789.4-2016), respectively. The results showed that Salmonella strains of 8 different serotypes were amplified successfully by the developed LAMP assay. And, it was 1000-fold more sensitive than the conventional PCR with the analytical sensitivity of 8×102 copies/μL of the standard sample of invA-plasmid. The results were visualized directly by adding Calcein/MnCl2 into the LAMP reaction tube and the positively amplified products turned green after an incubation of 2 min. In the parallel detection, the positive rate of Salmonella by the LAMP assay was highly correlated with the routine China national standard method. The results of the study demonstrated that the developed LAMP assay is a simple, rapid, strongly specific, highly sensitive and visual detection method for Salmonella.