Human serum resistance of <i>Escherichia coli</i> XL1Blue strains carrying the plasmid pUC19 and its derivatives harboring <i>ail</i> or <i>pagC</i> genes.

<p>Overnight grown bacteria were tested for viability at 37°C in 50% serum (black histograms) or heat-inactivated serum (hatched histograms). The resistance was expressed as the difference in log kill between XL1-Blue harboring pUC19 incubated in 50% human serum and XL1Blue harboring the recombinant plasmid incubated either in 50% human serum or heat-inactivated serum. Means and standard errors of results from triplicate experiments are shown.