Serum resistance analysis. (A) Heat map depicting the 56 essential serum resistome genes in our data set containing 139 strains belonging to ST38, ST405, ST648, and ST131 (clades A, B, and C). Black indicates a positive hit with identity of ≥70% and query coverage of ≥75%. (B) Serum resistance assay. Genome-wide screening of serum resistance genes revealed that few essential genes were missing from non-ST131 (ST38, ST405, and ST648) genomes, but the levels of phenotypic serum resistance were found to be comparable among all four STs.