TABLE 1.

Summary of low-dose oral infection in neonatal rats^a

E. coli K1 strain	Rat pup no.	Viable count of bacteria in:
		Colon (CFU/g)	Liver (CFU/g)	Spleen (CFU/g)	Blood (CFU/ml)
E44 (wild type)	1	1.4 × 107	8.5 × 107	3.0 × 108	3.0 × 104
	2	3.0 × 107	6.3 × 106	2.5 × 105	1.5 × 104
	3	2.6 × 107	1.7 × 105	2.5 × 105	1.5 × 104
	4	1.0 × 104	1.2 × 103	5.0 × 103	4.0 × 102
JLB9(traJ)	1	1.1 × 107	0	0	0
	2	2.0 × 104	2.5 × 103	5.0 × 103	0
	3	9.0 × 106	0	0	0
	4	1.2 × 109	3.3 × 103	0	0
	5	4.0 × 106	0	0	0
	6	1.9 × 107	0	2.5 × 103	0

^aOral doses of 10⁴ bacteria were given to neonatal rat pups [E44, n = 4; JLB9(traJ), n = 6]. Indicated tissues were collected from infected animals day 3 postinoculation, and viable counts were determined. Data are presented as CFU per gram of tissue or per milliliter of blood. Data presented are representative of several experiments with similar results.