Abstract: In this study, a loop-mediated isothermal amplification (LAMP) assay combined with propidium monoazide (PMA) treatment was developed for the rapid and efficient detection of Staphylococcus aureus with sublethal injury. The sensitivity of PMA-LAMP was investigated by artificially contaminating food samples including frozen dumplings and milk powder with S. aureus. The results showed that a concentration of 3 μg/mL PMA was optimal for completely restraining the amplification of 1.2 × 107 copies/mL of DNA from dead S. aureus which was exposed to a 650 W halogen lamp for 5 min. PMA-LAMP could achieve the specific detection of the unique nuc gene of S. aureus with sublethal injury at a constant temperature of 65 ℃ within 60 min with a sensitivity of 34 CFU/mL. In addition, the PMA-LAMP assay was proved efficient by using it to detect the viable cells in artificially contaminated samples, with a sensitivity of 17 CFU/mL for artificially contaminated milk powder and 1.70 × 102 CFU/mL in artificially contaminated frozen dumplings. It can be concluded that the PMA-LAMP assay can efficiently detect S. aureus with sublethal injury and provide a new technique for detecting S. aureus in food samples.

Key words: food safety, Staphylococcus aureus, sublethal state, propidium monoazide-loop-mediated isothermal amplification (PMA-LAMP), rapid detection