TABLE 1.
Comparison of the MPN method and real-time PCR for enumeration of salmonellae in a food sample
| Parameter | MPN method | Real-time PCR |
|---|---|---|
| Detected units | CFU | Nucleic acid (DNA), genome equivalents, can be correlated to CFU |
| Method | Based on horizontal detection method | Based on CT values of Salmonella DNA |
| Duration | 4-5 days | Approx 12 h |
| Approx cost (including personnel)a | Three-tube MPN (three dilutions), 500 €; five-tube MPN (three dilutions), 750 € | 300 € (three replicates) |
| Quantitation limit | Three-tube MPN (three dilutions), 3.0 MPN/g; five-tube MPN (three dilutions), 1.8 MPN/g | Approx 1 cell in 10 g |
| Precision (confidence limits) | For 1.8 MPN/g, 0.009 (low) to 6.8 (high) | No sufficient data yet available; ranges of 1 to 10, 10 to 100, and 100 to 1,000 cells have been reported |
| Automation possible | No | Yes |
| Standard curve setup necessary | No | Yes |
a
The cost for the personnel can vary between countries. The higher the cost for personnel, the higher the expected cost for the MPN or real-time PCR method. The calculation is based on the cost in a well-developed European country (e.g., German scale and charges of fees for medical services [http://www.e-bis.de/goae/defaultFrame.htm]).