Invasion of differentiated T84 cells by aEPEC 1551-2 after tight junction disruption by EGTA treatment. Monolayers were infected for 6 h (aEPEC) and 3 h (tEPEC). S. enterica sv Typhimurium and S. flexneri were used as controls and monolayers were infected for 4 h and 6 h, respectively. Results of percent invasion are the means ± standard error from at least three independent experiments performed in duplicate. * P < 0.05 by an unpaired, two-tailed t test.