Table 2.
Results of lab tests in milk, cheese, and environmental samples.
| Outbreak A | Outbreak B | |
|---|---|---|
| Milk samples | ||
| Raw milk SPC (log10 CFU/mL) | ||
| (1) Government dairy pool | 3.90 | n/a |
| (2) Local farm—cow | n/a | 3.00 |
| (3) Local farm—goat | 4.43 | n/a |
| Raw cow milk L.m. | Absent | Absent |
| Raw cow milk pH | NT | 6.8 |
| Pasteurized cow milk phosphatase | Negative | Negative |
| Cheese samples | ||
| Number of cheese samples L.m. + (tested) | 16 (25) | 22 (29) |
| Number of varieties + (number of lots+) | 8 (12) | 3 (3) |
| L.m. counts (median log10 CFU/g) | 2.0 | 2.0 |
| L.m. counts (range log10 CFU/g) | <2 to 9.4 | <2 to 9.0 |
| Environmental samples | ||
| In the plant—ingredients | ||
| Number of L. spp. + (tested) | 2 (33) | 2 (32) |
| In the plant—surfaces | ||
| FCS number of L spp. + (tested) | 3 (17) | 0 (5) |
| NFCS number of L spp. + (tested) | 2 (23) | 0 (17) |
| Outside the plant | ||
| Number of L spp. + (tested) | 1 (1) | 4 (7) |
| On the hobby or dairy farm | ||
| Number of L spp. + (tested) | 12 (14) | 6 (14) |
| Number of environmental L.m. + (tested) | 17 (88) | 14 (75) |
SPC, standard plate count; NT, not tested; n/a, not applicable; L.m., Listeria monocytogenes; L. spp., Listeria species (L. innocua, L. ivanovii or L. seeligeri); FCS, food contact surface; NFCS, nonfood contact surface.