TABLE 6.

Recovery of E. coli O157 strain from the spiked minced beef by IMS

Expt no.	No. of E. coli cells inoculated		Preenrichment culture				Solution used for:		After IMS
			MacConkey agar (cells/ml ± SD)						MacConkey agar (cells/ml ± SD)
	O157KB2 Rifr	Non-O157 E. coli cellsb	Total cells	Rifampin selection	Nalidixic acid selection	Ratio of cells (Rifr:Nalr)	IMS	Washing	Total cells	Rifampin selection	Nalidixic acid selection	Ratio of cells (Rifr:Nalr)
A	85 ± 28	74 ± 3	(1.9 ± 0.4) × 107	(4.8 ± 1.4) × 105	(3.0 ± 0.8) × 105	1.6:1	BPW	PBS-Tween 20	(4.2 ± 0.1) × 105	(5.4 ± 1.4) × 104	(1.0 ± 0.1) × 103	5.4 × 101:1
							CMQ	CMQ	(1.6 ± 0.2) × 104	(5.6 ± 1.3) × 103	0a	>5.6 × 103:1
B	85 ± 28	(74 ± 3) × 101	(3.8 ± 0.2) × 107	(4.4 ± 0.6) × 104	(2.6 ± 0.2) × 105	1.7 × 10−1:1	BPW	PBS-Tween 20	(1.4 ± 0.4) × 105	(7.6 ± 1.5) × 103	(9.4 ± 2.3) × 102	1.8 × 101:1
							CMQ	CMQ	(1.1 ± 0.1) × 104	(1.6 ± 0.3) × 103	5 ± 10	3.2 × 102:1
C	85 ± 28	(74 ± 3) × 102	(2.2 ± 0.2) × 107	(8.0 ± 1.0) × 104	(3.4 ± 0.4) × 106	2.5 × 10−2:1	BPW	PBS-Tween 20	(8.1 ± 1.1) × 104	(1.2 ± 0.04) × 104	(6.8 ± 0.3) × 103	1.7:1
							CMQ	CMQ	(6.3 ± 0.7) × 103	(2.7 ± 1.0) × 102	0a	>2.7 × 102:1
D	60 ± 2	(97 ± 2) × 102	(4.0 ± 0.6) × 107	(9.0 ± 4.6) × 104	(1.8 ± 0.4) × 107	5.1 × 10−3:1	BPW	PBS-Tween 20	(2.2 ± 0.4) × 105	(5.4 ± 1.0) × 104	(4.2 ± 0.3) × 104	1.3:1
							CMQ	CMQ	(4.3 ± 0.6) × 103	(3.2 ± 0.7) × 102	5 ± 10	6.4 × 101:1
E	60 ± 2	(97 ± 2) × 103	(9.4 ± 0.6) × 107	(4.6 ± 1.0) × 104	(1.1 ± 0.1) × 108	4.3 × 10−4:1	BPW	PBS-Tween 20	(4.2 ± 0.4) × 105	(1.9 ± 0.1) × 104	(3.7 ± 0.02) × 105	5.0 × 10−2:1
							CMQ	CMQ	(7.3 ± 0.3) × 103	(2.1 ± 0.1) × 103	(3.1 ± 0.9) × 102	6.8:1
F	0	0	NDc	NDc	NDc	NDc	BPW	PBS-Tween 20	(8.5 ± 0.9) × 104	0a	0a

^aThere were no cells in the 0.2-ml cell suspension. 

^bIn experiments D through F, the non-O157 E. coli strain used was V9 Nal^r. 

^cND, not determined.