Abstract: To enumerate Salmonella in meat of livestock and poultry rapidly and accurately by using propidium monoazide(PMA) combined with real-time fluorescence quantitation polymerase chain reaction(qPCR). The light exposure time and the concentration of PMA were optimized to establish PMA-qPCR. The standard curve was established by standard plasmid. The sensitivity and specificity were investigated. This method was used for the quantitation determination of Salmonella in livestock and poultry meat. The amplification of DNA derived from Salmonella dead cells could be inhibited without affecting the viable cells when PMA was at a dose of 15 μg/mL and exposed for 5 min. The cycle threshold values(Ct) and standard plasmid model cell copy number presented the satisfactory linear, and the correlation coefficient r² approached 0.997 9. This method could detect as low as 10 copies/reaction. The minimum detection level was 21 copies/μL by PMA-qPCR. In artificial chicken samples, PMA-qPCR could detect as low as 10³ CFU/mL. It was possible to quantify viable Salmonella in meat of livestock and poultry by PMA-qPCR.

Key words: Salmonella, Viable bacterium, Propidium monoazide, Real-time fluorescence quantitation polymerase chain reaction, Livestock and poultry meat