TABLE 3.
Virulence of H. somnus parent and recombinant strains in mice
| Strain | Challenge dose (CFU/mouse [107]) | No. of mice dead/total (% mortality)a | Bacteremiab (CFU/ml of blood [105]) |
|---|---|---|---|
| 738 | 1.1 | 6/8 (75)c | 3.7 |
| 738-lob2A1::Km | 1.0 | 1/9 (11)d | 1.7e |
a
By 48 h postchallenge.
b
Ten microliters of blood was obtained from the tail vein of each surviving mouse 6 h after challenge, diluted 1:10 in PBS, and inoculated onto blood agar.
c
In two mice, approximately 20% of the inoculum leaked out of the injection site. All mice that died did so within 30 h postchallenge.
d
This mouse died at 32 h postchallenge. The difference in mortality is significant (P = 0.0152).
e
The difference in bacteremia is significant (P = 0.0014). Both surviving mice challenged with strain 738 remained bacteremic at 30 h postchallenge, whereas only one of eight surviving mice challenged with strain 738-lob2A1::Km remained bacteremic at this time.