TABLE 3.

Transbullar homologous challenge with wt NTHI strain BCH-3 and an otherwise isogenic BCH-3 ompP1 mutant

Challenge strain	Immunogen	No. of animals with culture-positive middle-ear fluid/no. challenged (%), Pa, on day:
		2	4	6	8	10	14	18
wt BCH-3	rP1BCH-3 + adjuvant	1/20 (5)	8/18 (44)	7/18 (39)	5/16 (31)	5/16 (31)	2/16 (12)	2/16 (12)
	Adjuvant alone	4/4 (100), 0.001	4/4 (100), 0.067	4/4 (100), 0.045	4/4 (100), 0.026	4/4 (100), 0.026	3/4 (75), 0.032	2/2 (100), 0.039
	Nonimmunized	2/2 (100)	2/2 (100)	2/2 (100)	2/2 (100)	1/1 (100)	1/1 (100)	1/1 (100)
BCH-3 ompP1 mutant	rP1BCH-3 + adjuvant	8/8 (100)	8/8 (100)	8/8 (100)	8/8 (100)	8/8 (100)	6/7 (86)	4/6 (67)
	Adjuvant alone	3/4 (75), 0.333	3/4 (75), 0.333	3/4 (75), 0.333	3/4 (75), 0.333	2/3 (67), 0.273	2/3 (67), 0.533	2/3 (67), 0.774
	Nonimmunized	2/2 (100)	2/2 (100)	2/2 (100)	2/2 (100)	2/2 (100)	2/2 (100)	1/2 (50)

^aP values are based on a comparison of data for chinchillas immunized with rP1 plus adjuvant with those for chinchillas immunized with adjuvant alone, as determined by the Fisher exact test (80). Note that the incidence of culture-positive effusions from chinchillas immunized with rP1 plus RIBI adjuvant and challenged with wt BCH-3 was statistically significant. The incidence of culture-positive effusions from the contralateral unchallenged ears (bilateral effusion) was 5% in the group challenged with wt BCH-3 and 62% in the group challenged with the isogenic BCH-3 ompP1 mutant on days 6 and 8 (P = 0.0045).