41 ± 0.12 °C (n = 30); L. ivanovii, 83.90 ± 0.04 °C (n = 10); L. seeligeri, 84.32 ± 0.08 °C Selleck PS341 (n = 10); L. grayi, 85.03 ± 0.05 °C (n = 10); L. monocytogenes, 85.52 ± 0.13 °C (n = 30); and L. welshimeri, 86.15 ± 0.05 °C (n = 10; Fig. 2b). Thus, the Q-PCR and HRM analysis

specific to Listeria was applied and able to discriminate among the six Listeria species correctly. Listeria welshimeri was chosen to evaluate the sensitivity of the assay via a 10-fold serial dilution. The results showed that when serial dilutions of positive plasmid containing the target gene from L. welshimeri were tested along with a blank control, the LLOD was approximately 5 copies μL−1 (Fig. 3a). Furthermore, the HRM analysis showed that the Tm values were species-specific to L. welshimeri regardless of the plasmid’s

concentration (Fig. 3b), and a linear regression of the data provided the formula: cycle threshold (Ct) = –3.245 × log find more (copies μL−1) + 33.23, to calculate the unknown concentration of gene copies (Fig. 3c). Separately, to determine the sensitivity of this approach in detecting Listera in food products, the juice was inoculated to contain L. monocytogenes at 10–107 CFU mL−1 to evaluate the sensitivity for artificially contaminated samples. The results demonstrated that the sensitivity of artificially contaminated samples was 102 CFU mL−1 (results not shown). Thirty artificially contaminated samples else were prepared by spiking juice, milk, cheese, and meat with Listeria species respectively. The results showed that 28 of these were correctly identified, including eight L. monocytogenes, five L. welshimeri, five L. innocua, five L. ivanovii, three L. seeligeri

and two L. grayi, and the correction rate was 93.3%. Two juice samples spiked with L. monocytogenes and L. seeligeri tested negative according to Q-PCR and HRM analysis. The earlier results were shown in Table 3. There have been several cases of L. ivanovii, L. seeligeri, L. welshimeri, and L. innocua infections in humans causing febrile diarrhea and bacteremia, indicating the pathogenic potential of these Listeria species in humans (Rocourt & Seeliger, 1985; Andre & Genicot, 1987; Perrin et al., 2003; Gasanov et al., 2005; Guillet et al., 2010). Recently, a case of L. ivanovii infection in a man with a kidney transplant was reported (Guillet et al., 2010). Therefore, the identification of Listeria species is of great importance for antibiotic therapy in clinic. We explored the use of a Q-PCR assay integrated with a postamplification HRM analysis for the identification of members of the Listeria genus. All the Listeria species displayed positive PCR amplification and HRM curves; other closely related organisms did not. Therefore, not only is this assay specific to Listeria species, but the Listeria species were also individually identified through characteristic HRM profiles simultaneously.