Rapid detection of Salmonella typhimurium by photonic PCR-LFIS dual mode visualization

Salmonella spp., as one of the foodborne pathogens, is a severe threat to global public health. Rapid screening of salmonella spp. in contaminated food with low infective doses is the key to preventing food poisoning. In this study, a fast visualization method for detecting Salmonella typhimurium (S. typhimurium) was developed based on photonic PCR and AuNPs lateral-flow immunochromatography strip (LFIS). In addition, quantitative detection of target bacteria could be achieved by utilizing the photothermal effect of AuNPs, and the sensitivity could be improved by amplifying the photothermal signal. On the optimized conditions, the developed photonic PCR-LFIS assay was highly sensitive, with a detection limit as low as 19 cfu mL^-1 of bacteria in pure culture after laser irradiation, and highly specific, exhibiting no cross-reaction with Salmonella enteritidis, Listeria monocytogenes, Escherichia coli, and Staphylococcus aureus. Notably, S. typhimurium could be detected in pork, egg white, and milk without pre-treatment, with the recovery rates of the three samples between 81 % and 109 %. In conclusion, the photonic PCR-LFIS assay realizes sensitive, simple, and rapid detection of S. typhimurium.