Rapid and accurate AuNPs-sodium deoxycholate-propidium monoazide-qPCR technique for simultaneous detection of viable Listeria monocytogenes and Salmonella

Listeria monocytogenes and Salmonella are common pathogens in milk products that cause foodborne illness. Rapid and accurate detection is essential for effective control of their infections. In this study, the bioinformatics method was used to screen highly specific primers for L. monocytogenes (AX10_RS05385) and Salmonella (SEEPA511_RS03120), which were combined to construct a dual qPCR system. On this basis, propidium monoazide (PMA) was used to compensate the inability of qPCR to distinguish between viable and non-viable cells. The addition of sodium deoxycholate (SD) was utilized to maximally improve the inhibition efficiency of PMA. The gold nanoparticles (AuNPs) enhanced about 20% fluorescence signal of the qPCR system, thereby establishing a rapid, highly specific, and sensitive AuNPs-SD-PMA-qPCR detection technology. This method could accurately detect as low as 5 × 101 CFU/g L. monocytogenes and Salmonella in milk products after 6 h enrichment. Therefore, the AuNPs-SD-PMA-qPCR provided significant application value for simultaneous detection of viable L. monocytogenes and Salmonella in food.