FIG. 1.

FH binding to Y. enterocolitica O:3. (A and B) FH binding to YadA-positive and -negative strains, respectively, from 50% HIS was quantitated by ELISA. The wild-type strain FH-binding level was set to 100% (black bars), and those of the mutant strains are expressed relative to it. The data were obtained from three independent experiments. Error bars represent standard deviations. The factors expressed by the strains tested are marked as follows: YadA, Y; Ail, A; OAg, O; OC, C; the strains of the same phenotype obtained by different genetic methods are indicated by the subscript numbers 1, 2, and 3 (see Table 1 for details). The average OD₄₉₂ value for wild-type strain YeO3 was 0.74 ± 0.26 (range, 0.35 to 1.36). (C) Comparison of the ELISA and immunoblotting analyses of FH binding to selected Y. enterocolitica O:3 strains. (D) Presence of cross-reacting anti-YadA antibodies in goat antiserum against human FH (Quidel). Detection of FH bound to wild-type YeO3 bacteria by immunoblotting with the antiserum before and after adsorption with YadA-expressing bacteria is shown.