TABLE 3.
Adherence of strains of different serotypes in the presence of polyclonal serum that contains antibodies against intiminO157
| Straina | Serotype | Assay | Avg
no. of adherent bacteria ± 2SEM/10 HEp-2 cells in the presence
ofb:
|
Avg fold reduction in adherence by anti-intiminO157 serum (range)c | |
|---|---|---|---|---|---|
| Preimmune serum | Anti-intimin serum | ||||
| 86-24 | O157:H7 | I | 106 ± 25 | 10 ± 5 | 8.1 (4.7–10.9) |
| II | 50 ± 13 | 6 ± 2 | |||
| III | 158 ± 26 | 34 ± 10 | |||
| EDL933 | O157:H7 | I | 263 ± 66 | 30 ± 10 | 5.7 (3.7–8.9) |
| II | 195 ± 25 | 43 ± 12 | |||
| III | 220 ± 39 | 60 ± 21 | |||
| 97-3256 | O55:H7 | I | 109 ± 22 | 11 ± 6 | 10.3 (4.9–16.4) |
| II | 187 ± 49 | 11 ± 4 | |||
| III | 136 ± 34 | 28 ± 10 | |||
| 85-3007 | O111:NM | I | 57 ± 19 | 16 ± 12 | 3.0 (1.7–3.7) |
| II | 29 ± 9 | 17 ± 13 | |||
| III | 61 ± 19 | 17 ± 5 | |||
| H19 | O26:H11 | I | 58 ± 13 | 25 ± 7 | 1.9 (1.6–2.3) |
| II | 67 ± 17 | 37 ± 13 | |||
| III | 65 ± 15 | 41 ± 16 | |||
The numbers of bacteria added to the assay mixtures with respect to strain 86-24 (n = 1.2 × 107) were as follows: EDL933, n/2; 97-3256, n/15; 85-3007, n; H19, n/5. Serum dilutions were 1:140 for strains 86-24 and EDL933 and 1:90 for strains 97-3256, 85-3007, and H19.
Three independent assays were performed. For each assay, bacteria and HEp-2 cells were counted in 8 to 14 microscope fields per sample. The total number of HEp-2 cells counted in the set of fields observed for each sample was at least 100. The difference between the levels of adherence of the O157:H7 and O55:H7 strains in the presence of preimmune serum and polyclonal anti-intimin serum was significant, as calculated by Student's unpaired t test; P < 0.001 for each assay. For O111:NM strain 85-3007, the difference between the sera in assay II was not significant (P > 0.05); the P values for assays I and III were <0.01 and <0.001, respectively. For O26:H11 strain H19, the P values were <0.001, <0.02, and <0.05, respectively, for assays I to III.
The fold reduction in adherence in the presence of anti-intimin antiserum was calculated with respect to the preimmune serum control and was computed before rounding the numbers for each sample. The average fold reductions and ranges for the three assays are presented. For strains 95-3208, 97-3250, and E2348/69 there was no anti-intiminO157-specific reduction in adherence.