Cell permeability assay of S . Typhi and S . Typhimurium through H-T29 human cell line monolayers. (White diamonds) S. Typhimurium 14028s, (black squares) S. Typhi STH2370, (black triangles) S. Typhi STH2370/pNT005. The arrow indicates the time at which gentamicin was added. The results represent the average of three independent experiments. Each experiment was performed in duplicate. The values are expressed as the means ± SD of three independent experiments (asterisks represent p < 0.005). The CFU × ml-1 numbers from infected cells with S. Typhi carrying empty plasmid (pSU19 or pCC1) showed no differences with respect to the wild type strain (data not shown).