TABLE 6.

Duration and number of fecal E. coli O157:H7 in cattle after exposure to Trojan animals: Summer experiment^a

Animal	E. coli O157:H7 CFU/g of feces on postexposure day:
	0	5	9	15	22	29	36	47	54
TS1	0	0	0	1.5 × 102	2.0 × 104	2.2 × 104	1.0 × 103	E+b	0
TS2	0	0	E+	0	0	0	0	0	0
TS3	0	0	0	0	0	1.0 × 102	1.5 × 102	0	0
TS4	0	5.0 × 101	0	0	0	0	2.0 × 103	0	0
TS5	0	0	0	0	0	5.0 × 102	0	0	0
TS6	0	1.0 × 102	E+	5.0 × 102	2.0 × 102	1.5 × 102	5.0 × 103	4.1 × 104	0
TS7	0	E+	0	0	4.0 × 104	8.5 × 103	1.0 × 102	E+	E+
TS8	0	0	5.0 × 101	0	E+	2.0 × 104	5.0 × 101	0	E+
TS9	0	0	E+	0	0	3.0 × 102	0	0	0
TS10	0	1.5 × 102	1.0 × 102	1.0 × 103	5.0 × 103	5.0 × 101	0	E+	E+
TS11	0	E+	0	0	0	E+	0	E+	E+
TS12	0	0	0	0	5.0 × 103	2.5 × 102	0	0	0
TS13	0	5.0 × 102	E+	5.0 × 102	E+	0	0	E+	E+
TS14	0	E+	0	0	0	0	E+	0	E+
TS15	0	0	0	0	0	E+	E+	0	E+
Trojan D	0	5.0 × 101	E+	0	2.5 × 104	2.0 × 102	0	0	0
Trojan E	0	1.8 × 103	3.0 × 103	1.5 × 105	1.1 × 104	7.5 × 102	0	E+	E+

^aFifteen 6-month-old Holstein steers were penned together in contact with two Trojan cattle inoculated orally with a single dose of 3.5×10¹⁰ CFU of a four-strain mixture of E. coli O157:H7, including equal amounts of ATCC 43894, WSU 180, WSU 400, and WSU 588 at day zero in June (summer).

^bE+, sample was positive by enrichment culture technique but not by direct culture technique; this indicates that the number of CFU/g was ≤50.