Adherence and biofilm assays with <i>E</i>. <i>coli</i> recombinant strains.

<p><u>Panel A</u>: <i>E</i>. <i>coli</i> strains were incubated with epithelial cells for 30 min at 37°C. Following this, cells were washed to remove unbound bacteria, lysed, diluted, and spread onto agar plates to calculate the number of bound bacteria. The results are expressed as the mean percentage (± standard error) of inoculated bacteria attached to A549 cells. The values in parentheses show the actual percentage. <u>Panel B</u>: <i>E</i>. <i>coli</i> strains were cultured in the wells of PVC microplates, stained with crystal violet, washed with deionized water, and the wells were photographed. The arrow shows biofilm formation, which was quantitated by extracting crystal violet with methanol and measuring absorbance at 570 nm. The results are shown in parentheses and are expressed as the mean (± standard error) absorbance. <u>Both panels</u>: The asterisks indicate that the increase in adherence and biofilm formation of <i>E</i>. <i>coli</i> carrying pBpaB, compared to <i>E</i>. <i>coli</i> harboring pBHR1ΔDra, is statistically significant (<i>P</i> values < 0.05, Mann-Whitney test).