TABLE 3.

Passive-transfer experiments demonstrating that immune sera from mice vaccinated with the batA KO mutant strain provide protective immunity against challenge with lethal doses of WT B. mallei

No. of independent experimentsa	Treatmentb	Total no. of mice challenged	% survivalc		% sterile immunityd
			Acute infection	Chronic infection
4	Immune serum	35	91	66	0
	Naive serum	34	12	3	0
	batA KO vaccination	38	63	56	0

^aImmune serum was generated for each independent experiment.

^bMice were administered 1 ml of serum intraperitoneally. Forty-eight hours later, the animals were challenged intratracheally with ∼10 LD₅₀ of WT B. mallei ATCC 23344 using a Microsprayer device. Mice vaccinated with 10⁴ CFU of the batA KO strain 30 to 45 days prior to challenge with WT bacteria were used as efficacy benchmarks.

^cAcute infection, 1 to 10 days postchallenge; chronic infection, 11 to 55 days postchallenge.

^dThe livers, spleens, and lungs of survivors were collected, homogenized, diluted, and plated onto agar medium to determine whether the tissues were colonized with WT bacteria.