Among isolates from patients developing HUS of this serotype (n = 12), all isolates were positive for IpfAO26 and all were negative for eibG, astA, cnf, fyuA and pic. Differences among the NSFO157 and SFO157 developing HUS were seen for ihaA, agn43EDL933, espP and toxB, which were present in all NSFO157 and absent from all SFO157. The gene discussed is NPHS1; the disease is hemolytic-uremic syndrome.