Virulence-gene scheme for defining ST131 E. coli virotypes.

aPositive and negative results obtained by PCR for ibeA (invasion of brain endothelium), iroN (catecholate siderophore receptor), sat (secreted autotransporter toxin), afa/draBC (Afa/Dr adhesins), afa operon FM955459, papG II (allele II of papG gene), papG III (allele III of papG gene), cnf1 (cytotoxic necrotizing factor type 1), hlyA (alpha-hemolysin), cdtB (cytolethal distending toxin) and neuC-K1 (K1 variant of group II capsule).bMost isolates of virotype A and B are sat-positive.cIsolates of virotype D3 carry genes sat and afa/draBC, or at least one of them. In addition, some afa/draBC strains are positive for afa operon FM955459.