TABLE 3.

Ct and end fluorescence (dR) values for stx1, stx2, and the position 93 uidA SNP of E. coli O157:H7/H⁻ with four amplification parameters sets^a

Gene and isolate	Genotype	Result obtained with amplification parameter set:
		A		B		C		D
		Ct	dR	Ct	dR	Ct	dR	Ct	dR
stx1
EDL 933	+	20.14	131.115	19.59	182.974	20.89	112.544	22.36	76.967
CFSAN$400	+	18.98	143.727	18.76	209.545	19.79	129.558	20.52	88.951
ATCC 43889	−	−	0.112	−	−1.916	−	−0.572	−	0.216
C600	−	−	0.938	−	−2.059	−	1.171	−	−2.317
ATCC 13337	−	−	1.094	−	2.505	−	1.288	−	−1.102
Neg. control	−	−	1.202	−	−1.314	−	4.606	−	−0.855
stx2
EDL 933	+	18.8	235.545	18.46	336.727	19.76	149.934	−b	4.127b
CFSAN$400	−	−	−1.075	−	0.806	−	−0.580	−	−2.229
ATCC 43889	+	18.1	315.091	17.59	361.455	18.91	246.909	21.36	89.976
C600	−	−	0.402	−	−1.644	−	0.351	−	0.4498
ATCC 13337	−	−	−0.074	−	−0.389	−	−0.383	−	0.785
Neg. control	−	−	−0.276	−	1.405	−	0.545	−	−1.384
uidA
EDL 933	+	22.14	91.467	21.12	110.560	23.76	75.75	23.82	86.992
CFSAN$400	−	−	2.185	−	2.313	−	1.606	−	1.633
ATCC 43889	+	20.77	117.005	19.97	123.825	21.56	101.536	21.37	128.908
C600	−	−	5.138	−	5.084	−	6.649	−	4.009
ATCC 13337	−	−	0.728	−	2.201	−	0.450	−	−0.760
Neg. control	−	−	0.660	−	−1.343	−	−0.143	−	−0.210

^aMultiplex PCR conditions were as described in the text; for the conditions that correspond to parameter sets A, B, C, and D, see Table 2. +, positive; − and Neg., negative.

^bFalse-negative result.