Rapid and visual detection of viable Staphylococcus aureus in pork and pork products by PMA and saltatory rolling circle amplification

The aim of this study was to establish a rapid and visual nucleic acid isothermal amplification method for the detection of viable Staphylococcus aureus (S. aureus) in pork and pork products. The method was based on saltatory rolling circle amplification (SRCA) combined with propidium monoazide (PMA). Eighteen S. aureus strains and 29 non-S. aureus strains were used for the specificity evaluation. The sensitivity and detection limit of PMA-SRCA assay through fluorescence visualization were 2.6 x 10(1) CFU/mL and 6.6 x 10(1) CFU/mL, respectively. Compared with PMA-PCR assay, the PMA-SRCA method by fluorescence visualization exhibited a 1000-fold higher sensitivity. A total of 123 pork samples were tested for S. aureus contamination, and the results indicated that the relative sensitivity, specificity and accuracy of PMA-SRCA method were 100, 99.12 and 99.19%, respectively, compared with ISO method. In conclusion, the PMA-SRCA assay can reduce the false-positive detection rate of S. aureus in pork and pork products.