Table 3.
Quantification of genomic DNA extracted from pure culture and spiked milk sample.
| Conc. (CFU/mL) | Pure Culture 1 | Spiked Food Sample | ||
|---|---|---|---|---|
| qPCR (Ct) | ddPCR (Copies) | qPCR (Ct) | ddPCR (Copies) | |
| 108 | 16.37 ± 0.04 (9) | Saturated 2 | 16.13 ± 0.08 (9) | Saturated |
| 107 | 19.83 ± 0.03 (9) | Saturated | 19.52 ± 0.05 (9) | Saturated |
| 106 | 23.37 ± 0.02 (9) | 3287.78 ± 106.98 (9) | 23.46 ± 0.07 (9) | 4310 ± 295 (9) |
| 105 | 27.08 ± 0.15 (9) | 318.44 ± 10.49 (9) | 27.44 ± 0.12 (9) | 427.22 ± 60.31 (9) |
| 104 | 30.67 ± 0.08 (9) | 31.64 ± 1.9 (9) | 31.25 ± 0.16 (9) | 40.46 ± 6.58 (9) |
| 103 | 34.11 ± 0.31 (9) | 3.42 ± 0.62 (9) | 34.79 ± 0.3 (9) | 3.98 ± 0.59 (9) |
| 102 | ND 3 | 0.4 ± 0.11 (9) | ND | 0.25 ± 0.14 (9) |
1 Mean ± standard deviation (number of positive replicates on nine replicates analyzed). 2 DNA concentration at which the signal of the ddPCR assay was saturated. 3 ND, not detectable.