Table 4. Heterogeneity of PCR products related to the H.pylori hpyV and hpyIVA R-M systems, according to strain phenotype.
| Phenotypic susceptibility to RE | No. of strains examined | Methylase product | Number of strains by size of RM productb | |||
|---|---|---|---|---|---|---|
| Sizea | Number of strains | Expected | Truncatedc | None | ||
| TaqI (R.HpyV)-resistant | 10 | Expected | 10 | 4d | 3e | 3 |
| -susceptible | 16 | Expected | 7 | 6 | 0 | 1 |
| Truncated | 3 | 0 | 0 | 3 | ||
| None | 6 | 5 | 0 | 1 | ||
| HinfI (R.HpyIVA)-resistant | 10 | Expected | 10 | 5 | 4 | 1 |
| -susceptible | 55 | Larger | 2 | 1 | 1 | 0 |
| Expected | 21 | 7 | 11 | 3 | ||
| Truncated | 7 | 0 | 4 | 3 | ||
| None | 25 | 4 | 18 | 3 | ||
aUsing primers HP0260/HP0261 for hpyVM, expected = 1156 bp; using primers F2/R2 for hpyAIVM, expected = 914 bp.
bUsing primers HP0259/HP0262 for hpyVRM region, expected = 1889 bp; using primers F3/R3 for hinfIRM, expected = 2524 bp.
cUsing primers F3/R3 for the hpyAIVRM system, all 38 truncated products are ∼200 bp, which is the size of the ‘empty site’ product.
dFor strain 60190, which has known R.TaqI (R.HpyV) activity, the product is the expected 2.1 kb.
eUsing primers HP0259F and HP0262R for the hpyVRM system, all three truncated products are ∼250 bp, which is the size of the ‘empty site’ product.