TABLE 8.
Influence of preenrichment incubation time and bacterial population in the amplification of PCR product specific to B. cereus
| Sample or parameter | Preenrichment incubation in nutrient broth (h) | PCR band amplified when initial inoculum level was in the rangea or CFU per g of cooked-rice homogenateb:
|
||||||
|---|---|---|---|---|---|---|---|---|
| 2.4 × 104 | 2.4 × 103 | 2.4 × 102 | 2.4 × 101 | 2.4 | 0.24 | 0 | ||
| Food homogenate | 0 | − | − | − | − | − | − | − |
| 6 | + | + | + | − | − | − | − | |
| 15 | + | + | + | + | + | + | − | |
| Population | 0 | 2.4 × 104 | 2.4 × 103 | 2.4 × 102 | 2.4 × 101 | 2.4 | 0.24 | 0 |
| 6 | 9.0 × 106 | 4.6 × 105 | 4.0 × 104 | 9.7 × 103 | 1.5 × 103 | 2.0 × 102 | 0 | |
| 15 | 3.6 × 107 | 2.3 × 107 | 3.8 × 107 | 4.3 × 107 | 6.8 × 107 | 7.7 × 107 | 0 | |
a
−, 365-bp amplified product specific to B. cereus is not seen; +, 365-bp amplified product is seen.
b
Since cooked rice was used as a sample, no culturable food microflora was observed, and the counts given are for B. cereus.