TABLE 2.

stx genes in 173 STEC isolates and toxin production of the strains

Method and related stx genes	No. (%) of strains [n = 173]	No. of samples with indicated titers of Stx toxin
		≤1:2	1:4-1:16	1:32-1:64	≥1:128
PCR for stx according to Bastian et al. (1) and Lin et al. (27)
Positive strains	168 (97)	3	11	47	117
Weak positive strainsa	3 (2)	0	0	1	2
Negative strainsa	2 (1)	1	0	1	0
stx genes detected after restriction (HincII and AccI)b
stx1	28 (16)	0	1	18	9
stx1 and stx2 or stx2 variant	10b (6)
Stx1 titers		0	1	9	0
Stx2 titersc		0	2	2	6
stx2 and stx2c	72 (42)	0	0	0	72
stx2	36 (21)	0	1	13	22
stx2c	9 (5)	0	4	3	2
stx2vhb	5 (3)	1	0	0	4
stx2 and stx2vhb	3 (2)	0	0	1	2
Undigestible	5d (3)	2	2	1	0
PCR for stx2d according to Piérard et al. (37)
Positive strains	2d (1)	1	1	0	0
Negative strains	171 (99)	3	11	49	119
stx genes detected after restriction (HaeIII and PvuII)e
stx2d-Ount	2d (1)	1	1	0	0

^aThis result was obtained repeatedly.

^bNo stx_2e, stx_2ev, stx_2vO111, or stx_2vOX392 genes were detected.

^cThe corresponding stx₂ genes were stx_2c (titers of 1:4 to 1:16 [two strains], 1:32 to 1:64 [two strains], and ≥1:128 [two strains]), stx₂ (titer of ≥1:128 [one strain]), stx_2vhb (titers of ≥1:128 [two strains]), and stx₂ and stx_2vhb (titer of ≥1:128 [one strain]).

^dTwo undigestible strains were positive for stx_2d-Ount.

^eNo stx_2d-OX3a genes were detected.