RESUMO
Thirty-four hemolytic uremic syndrome (HUS) patients and ninety-five family members were studied to determine the frequency of infection with verocytotoxin-producing Escherichia coli (VTEC) in household contacts using three diagnostic criteria: VTEC strains isolation and characterization, detection of free fecal VT (FVT) and VT-neutralizing antibodies (VT-NAbs). Gastrointestinal tract symptoms occurend in one to six family members in 8 (23.5 per cent) of the index cases, the week before admission to hospital or simultaneously. The control group consisted of 34 children with acute gastroenteritis who did not develop HUS. Cumulative evidence of VTEC infection was found in 13 (38.2 per cent) of 34 HUS patients, in 30 (31.6 per cent) of 95 family members and in 10 (29.4 per cent) of 34 control children. The serotypes of VTEC isolated were O157:H7 and O25: H2. The prevalent VT type was VT2 in VTEC and FVT; and VT1 in VT-NAbs. Both parents had the same infection rate by fecal toxin or serological data (11.1 per cent FVT, 32 per cent VT-NAbs). These were higher than those detected in siblings (6.2 per cent FVT, 23.5 per cent VT-NAbs) and grandparents (0 per cent FVT, 18 per cent VT-NAbs). Of 16 patients without evidence of infection, 3 had household contacts with FVT and 13 with VT-NAbs. Our results show the wide dissemination of VTEC in the population of Argentina and that family members of HUS patients are usualy infectd. Therefore, person-to-person transmission may play an important role in the high incidence of HUS in our country.