FIG. 3.

Effects of spr deletion on the RS218-ΔnlpI mutant and the wild-type strain in terms of their abilities to interact with HBMECs. Hatched and filled bars indicate relative association and invasion frequencies, respectively, compared to the wild-type strain RS218, which was set at 100%. The association and invasion frequencies of the wild-type RS218 were 21% ± 3% and 0.75% ± 0.06%, respectively. The data shown are representative of three independent experiments done in triplicate. The results were shown as means ± the SD. *, P ≤ 0.01 between the nlpI or spr nlpI mutants versus the wild-type strain or spr mutant as determined by ANOVA.