UPEC survival in human serum.

<p>Bacteria (approximately 4×10⁸ CFU/ml) were incubated in fresh human serum for 90 min and colony counts were used to determine serum sensitivity index (SSI) for each strain, shown at the top of the graph. SSI of 0 represents a resistant strain; 1,2,3,4,5 represent equivalent reduction in log values of colony forming units (CFU/ml) post incubation with serum. The WT strains CFT073, 1177 and RS218 were resistant; CFT073<i>waaL</i>, 1177<i>waaL</i> and RS218<i>waaL</i> mutants were all highly sensitive to human serum (SSI; <i>P</i><0.05, paired t test) and the complemented strains (<i>waaL</i>^C) were resistant. CFT073<i>kpsD</i> and RS218<i>kpsD</i> mutants displayed reduced sensitivity (SSI = 2 and 1, respectively); complemented strains (<i>kpsD</i>^C) were resistant. The 1177<i>kpsD</i> mutant was completely resistant to serum killing.