FIG. 6.

Adhesion to human epithelial cells. (A to C) Int407 cells infected with the parent strain (A), ΔetrA mutant LZ2 (B), or ΔeivF mutant LZ3 (C) and subjected to Hemacolor staining. Magnification, ×400. (D) Semiquantitative analysis of adherence. The number of microcolonies (a microcolony consisted of >10 adherent bacteria) per cell was calculated from 20 fields for each experiment, and the means were determined from three independent experiments. An average of 140 cells were examined in each field.