TABLE 2.
Protection conferred by immunization with live or killed P. multocida strains
| Straina | Immunization route | % Survival (no. of animals in group)b |
|---|---|---|
| None (BHIB) | i.p. | 0 (5) |
| None (BHIB) | i.m. | 0 (5) |
| AL18 (live) | i.p. | 90 (10)c |
| AL18 (live) | i.m. | 50 (10)c |
| AL18 (killed) | i.p. | 0 (5) |
| AL18 (killed) | i.m. | 40 (5) |
| M1404 (killed) | i.p. | 40 (5) |
| M1404 (killed) | i.m. | 0 (5) |
a
Mice were immunized with either live or killed P. multocida AL18 (acapsular mutant) or M1404 (wild type) in 0.05 ml of brain heart infusion broth (BHIB).
b
Mice were challenged with 120 CFU of wild-type P. multocida M1404, observed for signs of disease, and killed by cervical dislocation when deemed moribund, in accordance with animal ethics requirements. Sensitive mice usually succumbed within 36 h, and mice which survived for at least 1 week after challenge were deemed immune. There was no significant difference observed in time to death for sensitive mice.
c
Significant protection compared to nonimmunized controls (P < 0.05; Fisher's exact test).