Table 4.
Association between generic E. coli-contaminated spinach and risk factors assessed in the univariate mixed-effect logistic regression analysis with farm and visit as random effects
| Variable (comparison level) | Frequencya | Reference level | OR (95% CI)b | P valuec |
|---|---|---|---|---|
| Farm management factor | ||||
| Human | ||||
| toilets (yes)d | 930/955 | No | 0.08 (0.01, 0.99) | 0.049 |
| Farm and field conditions | ||||
| organic_certified (yes) | 175/200 | No | 0.05 (0.00, 0.65) | 0.022 |
| before_rotavated (yes) | 490/955 | No | 0.21 (0.08, 0.54) | 0.001 |
| tillage_time (>17 days) | 85/185 | ≤17 days | 0.02 (0.00, 0.16) | <0.001 |
| Fertilizers | ||||
| manure_application (yes) | 160/955 | No | 7.9 (1.6, 39.4) | 0.011 |
| manure_time (>200 days) | 60/140 | ≤200 days | 0.08 (0.01, 0.90) | 0.041 |
| manure_age (>13 wk) | 20/150 | ≤13 wk | 156.6 (0.2, 114,716.7) | 0.133 |
| manure_source (poultry farm) | 90/150 | Dairy farm | 11.4 (1.1, 123.5) | 0.045 |
| compost_application (yes) | 140/955 | No | 0.08 (0.00, 2.02) | 0.127 |
| Irrigation | ||||
| irrigation_time (>5 days) | 365/845 | ≤5 days | 0.17 (0.05, 0.59) | 0.005 |
| irrigation_source_pond (yes) | 20/955 | No | 24.4 (2.1, 280.1) | 0.010 |
| irrigation_source_well (yes) | 635/955 | No | 0.30 (0.06, 1.51) | 0.144 |
| irrigation_source_reservoirs (yes) | 160/955 | No | 0.08 (0.01, 0.40) | 0.002 |
| Equipment | ||||
| own_equipment (yes) | 865/955 | No | 9.1 (2.4, 34.6) | 0.001 |
| Planting_time (>66 days) | 465/955 | ≤66 days | 2.6 (1.3, 5.2) | 0.008 |
| Farm environmental factors | ||||
| Terrain, buffer zone, and proximity | ||||
| terrain (sloped) | 165/955 | Flat | 8.3 (2.5, 27.3) | <0.001 |
| buffer_fence (yes) | 165/895 | No | 4.8 (1.9, 12.0) | 0.001 |
| proximity_beef (yes) | 120/955 | No | 6.0 (0.5, 79.1) | 0.174 |
| proximity_poultry (yes) | 110/955 | No | 8.7 (0.9, 88.0) | 0.067 |
| proximity_forest (yes) | 60/955 | No | 0.11 (0.03, 0.43) | 0.002 |
| proximity_roadways (yes) | 895/955 | No | 0.07 (0.02, 0.28) | <0.001 |
| Domestic/wild animals | ||||
| wildlife_control (yes) | 505/910 | No | 5.0 (1.9, 13.2) | 0.001 |
| domestic_animal (yes) | 25/935 | No | 11.8 (1.1, 122.9) | 0.039 |
| Farm_location (Southwestern U.S.) | 480/955 | Western U.S. | 4.4 (0.8, 25.5) | 0.096 |
a
Frequency is the number of observations with the comparison level/total number of recorded observations for the variable.
b
OR (95% CI), odds ratio with 95% confidence interval.
c
Only variables with P values of <0.2 are shown.
d
The estimated OR (95% CI) value applies to each factor in the “hygiene-field status” group: toilet_training (yes versus no), washing_stations (yes versus no), field_grazed (no versus yes), and before_hay (no versus yes).