Establishment of real-time quantitative PCR-based methods for detection of Staphylococcus aureus in food / 军事医学科学院院刊

ABSTRACT

Objective To develop a sensitive,specific, simple and rapid quantitative real-time PCR (Q-PCR) assay for detection of Staphylococcus aureus with SmartCycler.Methods According to the nuc gene sequences specific to S.aureus, a pair of primers and one TaqMan probe were designed. An internal amplification control (IAC) which is a chimeric double-stranded DNA constructed from a fragment of the Listeria monocytogenes hly gene flanked by the nuc-specific target sequences was added to the reaction system. This IAC was detected using a second TaqMan probe labeled with a different fluorophore. The performance of the nuc-IAC Q-PCR was evaluated using artificially contaminated drinking water and commercial UTH whole milk samples spiked with ATCC 6538.Results The nuc-IAC assay could be used reliably for detection with a sensitivity of 5 copies of linear plasmid DNA per reaction, 10 fg of genomic DNA in 62.5% of the reactions or 50 cfu/ml S.aureus cells with 50% probability. The quantification was linear (r~2≥0.998) over a 6-log dynamic range, with a PCR efficiency over 0.967. The 5×10~2 CFU per 25 ml mimic sample of drinking water or milk could be detected by this assay consistently and quantifiably.Conclusion The nuc-IAC Q-PCR assay for S.aureus is developed. It could not only be applied for the quantitative detection of S.aureus, but also prevent the false negatives and underestimations of contamination loads due to PCR failure.