TABLE 3.
Protective effect of live negative marker vaccine upon A. pleuropneumoniae serotype 9 challenge
| Group | Challenge dose (CFU aerosolized per 5 pigs)a | Necropsy time (day) | No. of animals with lung lesions/total no.b | Arithmetic mean ± SD of lung lesion score | No. of animals with reisolation of A. pleuropneumoniae at post mortem analysis in:
|
Arithmetic mean ± SD of reisolation score | |||
|---|---|---|---|---|---|---|---|---|---|
| Tonsil | Lymph node | Lung
|
|||||||
| Pneumonic | Intact | ||||||||
| Vaccinatedc | 1.6 × 105 | 7 | 3/4 | 4.9 ± 5.4 | 1/4 | 4/4 | 3/3 | 3/4 | 1.5 ± 1 |
| 21 | 4/6 | 3 ± 5.6 | 2/6 | 1/6 | 2/4 | 2/6 | 1.4 ± 2.8 | ||
| Unvaccinated control groupd | 1.7 × 105 | 2 | 3/3 | 24.9 ± 3.1 | 3/3 | 3/3 | 3/3 | 3/3 | 7 |
| 21 | 2/2 | 3 ± 1.6 | 1/2 | 0/2 | 1/2 | 1/2 | 0.5 ± 0.7 | ||
a
A. pleuropneumoniae serotype 9 was grown to an optical density of 0.43 at 600 nm and then diluted 1:30,000 with sterile 0.9% NaCl solution; 13 ml of this dilution was aerosolized in the chamber. The numbers given are the CFU in 13 ml.
b
The lung lesion score was determined as described by Hannan et al. (23).
c
A. pleuropneumoniae sixfold mutant was grown to an optical density of 0.45 at 600 nm and diluted 1:30,000 with sterile 0.9% NaCl solution; 13 ml of this dilution was aerosolized in the chamber.
d
Three nonvaccinated control pigs died within 48 h after infection.