TABLE 4.

Protection against B. abortus 2308 provided to BALB/c mice after vaccination with B. abortus S19 or the B. abortus BAI129 cgs mutant^a

Challenge dose (CFU)	Vaccination strainb	Log CFU/spleen 1 wk p.i.c (mean ± SD)	Spleen wt (g) (mean ± SD)	Protectiond
109	None	8.60 ± 0.04	NDe	0.00
	S19	6.44 ± 0.03	0.51 ± 0.02	2.16
	BAI129	6.79 ± 0.03	0.44 ± 0.03	1.91
107	None	6.27 ± 0.10	0.34 ± 0.03	0.00
	S19	3.52 ± 0.01	0.19 ± 0.05	3.05
	BAI129	2.99 ± 0.56	0.14 ± 0.01	3.29
105	None	6.55 ± 0.05	0.20 ± 0.04	0.00
	S19	0f	0.18 ± 0.04	6.55
	BAI129	0f	0.13 ± 0.04	6.55

^aMice were inoculated intraperitoneally with 10⁴ CFU of B. abortus S19 or B. abortus BAI129. One month postvaccination, mice were challenged with different doses of B. abortus 2308. Eight week later, the animals were killed and their spleens were removed and weighed. Spleens were processed as described in Materials and Methods. 

^bVaccination doses were 10⁴ CFU. 

^cp.i., postinfection 

^dProtection = log CFU of control non-vaccinated mice − log CFU of vaccinated mice (15). 

^eND, not determined. 

^fDetection limit was 10² CFU.