The primer pair was designed using primer premier Navitoclax 5.0 software based on the L. monocytogenes ssrA gene (AF440343) in the conserved region. The primer set for the Q-PCR mixture containing the fluorescent binding dye

was designed to have no misprimings and no dimers. Also, the primer sequence was proved to be unique for Listeria species through a homology search using Basic Local Alignment Search Tool (blast; NCBI, NIH). The forward primer: 5′-CGT GCA TCG CCC ATG TGC-3′ and reverse primer: 5′-ATC TAC GAG CGT AGT CAC-3′ were provided by TaKaRa Biotechnology (Dalian, China). The Q-PCR was performed in a final volume of 25 μL containing 1× PCR buffer [10 mM Tris–HCl (pH 8.3), 50 mM KCl, 3.5 mM MgCl2, 250 mg L−1 bovine serum albumin], 200 μM each of dNTPs, 1× EvaGreen fluorescent dye (Huirui Bio-Tech, Shanghai, China), 0.4 μM of the forward and reverse primers, 2 U Taq DNA polymerase, and 2 μL genomic DNA (15–50 ng). selleck screening library The reaction was performed on a LightCycler 480 Q-PCR system (Roche Diagnostics, Indianapolis, IN). The

cycling conditions were one cycle at 94 °C for 2 min, 45 cycles at 94 °C for 15 s, and then one cycle at 60 °C for 45 s. After the above-mentioned steps, HRM analysis was performed. The HRM curve was generated through 0 s at 94 °C, 30 s at 60 °C, and continuous ramping (0.1 °C s−1) Exoribonuclease up to 90 °C. The melting profiles were created by HRM software with fluorescence normalization from the 82–88 °C region (LightCycler® 480 software). Double-distilled water was the blank control used in parallel with each experiment.

The construction of the plasmid followed a previously published protocol (Sambrook & Russell, 2001). Genomic DNA was extracted from L. welshimeri, and the PCR was performed as described earlier. The purified PCR products were inserted into a pGEM®-T vector (Promega, CA) and transformed into Escherichia coli JM109, according to the manufacturer’s instructions. Positive clones were confirmed via PCR and direct sequencing. The number of copies of plasmid per microliter was calculated according to the previously published formula (Guan et al., 2011). The positive plasmid was diluted for determining the lower limit of detection (LLOD). Each dilution series was repeated three times, and then a blank control was set up. The specificity and sensitivity of the results were based upon the melting curve analysis and Q-PCR amplification curve, respectively. A linear regression of the data would provide a formula generated through the attached software (LightCycler® 480 software). The ssrA gene or tmRNA, with both tRNA-like and mRNA-like functions, rescues stalled ribosomes and clears the cell of incomplete polypeptides and RNA species (Keiler et al., 2000; O’Grady et al., 2008).