TABLE 1.

Protective effect of passively transferred rabbit anti-tD15 antiserum against Hib in the infant rat model of bacteremia^a

Group	Rabbit serum	Anti-tD15 antibody titer	No. bacteremic/no. challenged	Mean CFU/2.5 μl of bloodb
1	Anti-tD15	51,200	2/10	30
2	Preimmune	<200	10/10	700
3	PBS	<200	9/9	1,250

^aFive-day-old infant rats were passively immunized s.c. with 0.1 ml of rabbit antiserum, immune serum, or PBS. Twenty hours later, the animals were challenged i.p. with freshly grown Hib strain MinnA (200 CFU in 0.1 ml) as described in Materials and Methods. The statistical significance of the difference in results obtained between antisera and preimmune sera (P = 0.0007) was established by Fisher’s exact test. 

^bDuplicate plating.