TABLE 2.

+, reduced adherence observed; −, no inhibition of adherence observed. The average reduction in adherence in the presence of anti-intimin_O157 polyclonal serum relative to preimmune serum (from three assays) was 8.1-fold; bacterial counts are presented in Table 3 in the context of other experiments. For the other polyclonal sera, bacterial counts were not determined; relative levels of adherence compared to preimmune sera were assessed microscopically. 

Serum from three of the four immunized mice reduced adherence of strain 86-24. 

The level of adherence in the presence of antibodies to the C-terminal third of intimin (anti-His-IntC_1/3) was an average of 4.4-fold lower than that in the presence of antibodies to the N-terminal region (anti-His-IntN_2/3). To determine the average fold reduction, three independent assays were performed; for each assay, bacteria and HEp-2 cells were counted in 11 or 12 microscope fields per sample. Each field contained at least 10 HEp-2 cells, although not every HEp-2 cell contained adherent bacteria. Thus, the following data for the three assays are presented as the average numbers of bacteria (± two times the standard errors of the means) per 10 HEp-2 cells (anti-His-IntN_2/3/anti-His-IntC_1/3): 230 ± 24/101 ± 21, 222 ± 36/43 ± 13; 255 ± 30/45 ± 9. In each experiment, the difference between adherence levels in the presence of the two antibody fractions was significant (Student's unpaired t test; P < 0.001).