TABLE 3.

Summary of all experiments of spleen colonization in mice immunized with WR201 and challenged 9 weeks later intranasally with 16M

No. of weeks after infection	No. infected/no. challenged (%) after immunization witha:		P valueb
	Saline	WR201
1	2/5 (40)	1/5 (20)	0.99c
2	9/10 (90)	3/9 (30)	0.020
4	14/17 (80)	4/18 (20)	0.006
8	21/25 (80)	6/25 (20)	<0.001
12 or 13	22/25 (90)	11/25 (40)	0.002

^aMice were immunized with WR201 or sham immunized with saline and challenged with 10⁴ CFU of 16M intranasally. Animals were euthanized at various times after infection for determination of number of splenic bacterial CFU. Limit of detection = 2 CFU. 

^bFisher's exact test. Data are pooled from experiments A through E. 

^cNot significant.