Table 3.
Pathogen prevalence in lettuce, soil, and seedling samples (presence /25 g) and in water samples (presence per liter) taken in greenhouses and open field farms.
| n a | Pathogen | PCR Screening b | Confirmed by Culture | |||
|---|---|---|---|---|---|---|
| GREENHOUSE FARM | Lettuce | 48 | Campylobacter spp. | 8.4% | ||
| Soil | 48 | EHEC | 4.2% | vt1, eae | ||
| Soil | 48 | EHEC | 4.2% | vt2, eae | ||
| Water source | 35 | Salmonella spp. | 2.9% | |||
| Water source | 35 | EHEC | 2.9% | vt1, vt2, eae | ||
| Water source | 35 | Campylobacter spp. | 20% | |||
| Water tap | 36 | Campylobacter spp. | 2.8% | |||
| OPEN FIELD FARM | Lettuce | 40 | Campylobacter spp. | 10% | ||
| Soil | 44 | Salmonella spp. | 2.4% | |||
| Soil | 44 | EHEC | 6.8% | vt2, eae | O157 | |
| Soil | 44 | EHEC | 6.8% | vt1, vt2, eae | O103, O157 | |
| Soil | 44 | EHEC | 6.8% | vt1, eae | O26 | |
| Water source | 33 | EHEC | 15.2% | vt1, eae | ||
| Water source | 33 | EHEC | 15.2% | vt1, eae | O111 | |
| Water source | 33 | EHEC | 15.2% | vt1, eae | O26 | |
| Water source | 33 | EHEC | 15.2% | vt1, vt2, eae | ||
| Water source | 33 | EHEC | 15.2% | vt1, eae | ||
| Water tap | 5 | Campylobacter spp. | 20% | |||
| Wash water | 7 | Campylobacter spp. | 57.1% | |||
a Number of samples checked; b PCR screening with Genedisc or the method of Posse et al. [41]; EHEC, E. coli strains possessing the vtx-coding genes vt1 or vt2 and the intimin-coding gene eae.