Resistance to serum killing among E. coli bloodstream infection isolates, stratified by multilocus sequence type (ST).

A serum bactericidal assay was performed on each E. coli isolate, and survival was determined by number of colonies in the serum-treated sample (either 25% or 50% serum) divided by the number of colonies in the negative serum control. The mean survival and range of survival values for each E. coli ST with ≥5 isolates in our study population are shown here. P-values were calculated with t-tests (e.g., proportion of surviving bacteria in ST12 relative to non-ST12 isolates). P-values ≤0.05 are in bold.