TABLE 2.
Toxic sample (2 MU) | Enterotoxicityb
|
||||
---|---|---|---|---|---|
Unheated control | Heated for 15 min
|
||||
90°C | 95°C | 100°C | 105°C | ||
STp (control)c | 0.151 (100) | 0.144 (100) | 0.067 (25) | 0.081 (25) | NT |
pEHSTN24 | 0.141 (100) | 0.105 (62) | 0.094 (50) | 0.079 (25) | 0.061 (0) |
pEHSTC22 | 0.127 (100) | 0.099 (57) | 0.089 (50) | 0.078 (25) | 0.067 (0) |
pEHProSTC28 | 0.154 (100) | 0.107 (62) | 0.095 (50) | 0.076 (20) | NT |
pSTC17 + pDSPH524 | 0.134 (100) | NT | 0.143 (100) | 0.102 (100) | 0.104 (66) |
The solid culture supernatant fractions of E. coli DH5α strains with the indicated plasmids were prepared, their titers were adjusted to 2 MU, and they were tested in the suckling mouse assay (5 to 10 mice per sample).
As described in Table 1, footnote a. Values are G/C ratios; the values in parentheses are scores expressed as percentages. NT, not tested.
Pure native STp toxin (Calbiochem) was adjusted in titer to 2 MU and used as a positive reference control.