TABLE 2.

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

Method and related stx genesNo. (%) of strains [n = 173]No. of samples with indicated titers of Stx toxin
≤1:21:4-1:161:32-1:64≥1:128
PCR for stx according to Bastian et al. (1) and Lin et al. (27)
    Positive strains168 (97)31147117
    Weak positive strainsa3 (2)0012
    Negative strainsa2 (1)1010
stx genes detected after restriction (HincII and AccI)b
    stx128 (16)01189
    stx1 and stx2 or stx2 variant10b (6)
        Stx1 titers0190
        Stx2 titersc0226
    stx2 and stx2c72 (42)00072
    stx236 (21)011322
    stx2c9 (5)0432
    stx2vhb5 (3)1004
    stx2 and stx2vhb3 (2)0012
    Undigestible5d (3)2210
PCR for stx2d according to Piérard et al. (37)
    Positive strains2d (1)1100
    Negative strains171 (99)31149119
stx genes detected after restriction (HaeIII and PvuII)e
    stx2d-Ount2d (1)1100
  • a This result was obtained repeatedly.

  • b No stx2e, stx2ev, stx2vO111, or stx2vOX392 genes were detected.

  • c The corresponding stx2 genes were stx2c (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]), stx2vhb (titers of ≥1:128 [two strains]), and stx2 and stx2vhb (titer of ≥1:128 [one strain]).

  • d Two undigestible strains were positive for stx2d-Ount.

  • e No stx2d-OX3a genes were detected.