TABLE 6.

Passive protection of infant rats with pediatric serum pools^a

Expt no.	Subject or pool no. (age [yr]) and serum sampleb	Dilution	Strain 4243 (OAc positive) (expt A)			Strain 4335 (OAc negative) (expt B)
			Antibody dose (μg/rat)c	No. of animals positive for bacteremia/ total no. tested	CFU/ml (geometric mean [103])	Ab Antibody dose (μg/rat)	No. of animals positive for bacteremia/ total no. tested	CFU/ml (geometric mean [103])
2	Subject 55 (adult)
	Pre	1:5	0.002	7/7	434	≤0.002	7/7d	>500
	Post	1:26	0.2	0/7	<0.001	0.14	0/7	<0.001
	Post	1:130	0.04	0/7	<0.001	0.03	3/7d	0.05
	Post	1:650	0.008	5/7	1.69	0.006	7/7	>500
	Pool 4 (2.6)
	Pre	1:2	<0.005	7/7	>500	≤0.005	7/7	>500f
	Post	1:1.4	0.2	5/5	>500	0.18	3/3	49f
	Post	1:5	0.04	7/7d	>500	0.05	7/7	>500
	Pool 3 (4.6)
	Post	1:2	0.6	0/5	<0.001	NDe	ND	ND
	Post	1:6	0.2	0/7	<0.001	0.15	3/7c	0.101
	Post	1:30	0.04	3/7	0.022	0.03	7/7	314
3	Negative control
	PBS			5/5	>500		5/5	>500g
	Subject 55 (adult)
	Post	1:26	0.2	0/5	<0.001	0.14	1/5	0.002
	Post	1:130	0.04	3/3	7.4	0.03	5/5	108
	Pool 3 (4.6)
	Post	1:6	0.2	4/5	0.04h	0.15	5/5	23g
	Post	1:30	0.04	5/5	197	0.03	5/5	>500
	Pool 2 (4.5)
	Pre	1:5	<0.02	5/5	>500	≤0.02	5/5	>500g
	Post	1:6	0.2	0/4	<0.001h	0.13	2/5	0.045
	Post	1:30	0.04	5/5	76	0.03	5/5	>500

^aExperiments 2A and 2B and experiments 3A and 3B were done on separate days. For description of pools, see footnote a of Table 3.

^bPre, preimmunization; post, postimmunization.

^cAntibody doses were calculated as described in footnotes b and c to Table 5.

^dOne rat in each of these groups was dead 18 h after bacterial challenge. These animals were presumed to be positive for bacteremia. For calculation of geometric mean CFU per milliliter, the dead animals were assigned values of 1,000,000 CFU/ml of blood.

^eND, not done.

^fP > 0.10 (for comparison of geometric mean CFU per milliliter after treatment with postimmunization serum pool 4 to that of animals treated with preimmunization serum).

^gP = 0.05 (for comparison of geometric mean CFU per milliliter after treatment with postimmunization serum pool 3 to that of the combined group of 10 animals treated with either preimmunization serum or PBS).

^hP < 0.03 (for comparison of geometric mean CFU per milliliter after treatment with antibody (0.2 μg/rat) from postimmunization serum pool 3 to that of animals treated with antibody (0.2 μg/rat) from postimmunization serum pool 2).