TABLE 1.
Effect of challenge dose on NP colonization and middle ear infection caused by NTHI 12 in chinchillasa
| Group | Challenge dose (CFU) | NP colonization
|
Middle ear infection (no. of animals infected/total no. of animals challenged) (%) | |
|---|---|---|---|---|
| No. of animals infected/total no. of animals challenged (%) | Mean CFU/25-μl nasal lavage | |||
| 1 | 108 | 7/7 (100) | 1,000 | 6/7 (86) |
| 2 | 105 | 7/7 (100) | 1,030 | 1/7 (14)c |
| 3 | 102 | 5/6 (83) | 325b | 0/6 (0)c |
a
Chinchillas (2 to 3 months old) were challenged intranasally with various doses of NTHI 12 as described in Materials and Methods. NP lavages were performed 4 days postinoculation. Middle ear infections were monitored at days 4 and 7 postchallenge by otoscopy and tympanometry.
b
Student’s unpaired t test. Statistical significance compared to the animals in groups 1 or 2 was found (P < 0.05).
c
Fisher exact test. Statistical significance compared to animals in group 1 was found (P < 0.05).