Table 1. Overview of the design and bacteriology and pathology findings of the in vivo experiment.
| Calf pair | Prechallenge antibody level1 | Bacterial challenge2 | Euthanasia date (DPI)3 | Nasal M. haemolytica4 (days positive/ days tested) | Lung M. haemolytica 5 (maximum CFU/100 mg) | Gross lung lesions6 (%) | Lung:heart weight ratio | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TAP | Water | OD | CFU | TAP | Water | TAP | Water | TAP | Water | TAP | Water | ||
| 1 | 1300 | 300 | 1.0 | 5x1010 | 1 | 1/1 | 1/1 | 0 | 2.0x109 | 1.1 | 10.0 | ||
| 2 | 900 | 500 | 0.5 | 2x109 | 3 | 2/3 | 3/3 | 4.5x106 | 2.0x102 | 7.7 | 0.1 | 2.00 | 1.92 |
| 3 | 1000 | 1600 | 0.5 | 4x109 | 4 | 2/4 | 3/4 | 0 | 0 | 0.1 | 0.7 | 1.65 | 2.15 |
| 4 | 3200 | 3100 | 0.5 | 2x109 | 2 | 2/2 | 2/2 | 0 | 2.0x108 | 1.1 | 22.0 | 1.92 | 2.13 |
| 5 | 2100 | 2800 | 0.77 | 9x108 | 7 | 4/4 | 3/4 | 2.5x107 | 5x104 | 3.7 | 0.9 | 2.33 | 1.93 |
| 6 | 3900 | 5400 | 0.5 | 2x109 | 4 | 4/4 | 4/4 | 0 | 0 | 0.7 | 0.1 | 1.82 | 2.23 |
1 Prechallenge antibody levels: the data suggest an absence of antibody to M. haemolytica leukotoxin, as the ELISA values were similar to those in fetal calf serum and lower than the range reported in conventional calves [4].
2 Bacterial challenge: quantification of Mannheimia haemolytica used for the challenge, based on the intended OD (600 nm) and by subsequent colony counts on agar (CFU administered to the calf).
3 Euthanasia date: calves were euthanized on the indicated number of days post-infection.
4 Nasal Mannheimia: nasal swabs were obtained dailyfor culture, and Mannheimia haemolytica was identified by colony morphology. The data show the number of days with positive cultures.
5 Lung Mannheimia: samples of cranioventral, caudoventral and caudodorsal lung were obtained at postmortem (plus sampling lesions when present), quantitatively cultured, and the number of Mannheimia colonies per 100 mg of lung tissue was determined.
6 Gross lung lesion score: The percentage of lung tissue affected by consolidation based on image analysis.
7 Calf pair #5 were challenged on day 0 (OD = 0.5, 9x108 CFU), then re-challenged on day 3 with 1x1010 CFU, and euthanized on day 8 post-infection. Only the clinical data prior to the time of re-challenge are presented.