Phage amplification-based technologies for simultaneous quantification of viable Salmonella in foodstuff and rapid antibiotic susceptibility testing

Salmonella, especially drug-resistant Salmonella poses a serious threat to food safety and human health. Herein, we proposed a rapid, accurate and sensitive phage amplification-based analysis (PAA) based on an isolated Salmonella phage T156 with broad host range and potent lysis ability for the quantification of viable Salmonella, as well as rapid antibiotic susceptibility testing. This assay has been successful applied to quantify viable Salmonella in food matrices such as milk and lettuce, with a detection limit of 1 colony forming units (CFU) /mL and high specificity for only detect live bacteria not dead bacteria. When combined with real-time PCR (qPCR), PAA-qPCR further reduced the detection time from 6.5 h to 3.5 h, with a detection limit of 10 CFU/mL and without complicate DNA extraction or purification process. Moreover, this assay could also specifically detect drug-resistant Salmonella, shortening the detection time from 24 h to 6.5 h. The results were consistent with that of the conventional paper disc diffusion method (DDM). These PAA methods were evaluated and applied for Salmonella quantification, as well as the detection of drug-resistant Salmonella, providing a promising platform to trace the foodborne pathogen in the complex food matrix, as well as the detection of drug-resistant Salmonella.