FIG. 1.

EAEC induces barrier disruption. (A) Infection with EAEC 042 causes a time-dependent decrease in TER of polarized T84 monolayers. Polarized T84 cells were infected in EAEC strain 042; Salmonella Typhimurium served as positive control for barrier disruption, and commensal E. coli strain HS and uninfected monolayers served as negative controls. Three hours after the addition of bacteria, the infection was terminated by aspiration of the apical compartment medium and addition of fresh medium containing gentamicin. TER was measured at 0, 3, 6, 14, and 24 h after infection. The figure represents an average of five separate experiments with each performed in triplicate wells. Error bars indicate one standard deviation of mean TER. Strain 042 and Salmonella cells were significantly different from HS and uninfected T84 cells 24 h after infection (P < 0.05 determined by ANOVA). (B) EAEC strain 042 effects on epithelial permeability are irreversible over 48 h. Polarized T84 cells were infected in triplicate for 3 h, followed by treatment with gentamicin as described for panel A. White bars represent TER at 24 h, and black bars represent TER at 48 h after the 3-h infection. Strain 042 and Salmonella cell effects on TER were significantly different from that induced by HS, from uninfected monolayers, and from either 042aafA mutant at both 24 and 48 h. *, P < 0.05 determined by ANOVA with Tukey's posttest.