TEMPORAL VARIATION OF GENOTYPES AND SEROT YPES OF ENTEROHEMORRHAGIC E-COLI ISOLATED FROM CHILEAN CHILDREN WITH ASYMPTOMATIC INFECTIONS OR HEMOLYTIC-UREMIC SYNDROME

Background: Infections by enterohemorrhagic E. Coli may be asymptomati c may cause diarrhea, sometimes bloody or a hemolytic uremic syndrome in 2 to 7% of children. These diseases appear sporadically or as outbr eaks. Host and agent factors influence the appearance of hemolytic ure mic syndrome. Aim: To study the distributions and prevalence of virule nce genes and enterohemorrhagic E. Coli serogroups isolated from Chile an children. Materials and methods: Thirty six strains isolated from c hildren with hemolytic uremic syndrome (8 obtained in 1988-1989, 175 o btained in 1990-1993 and 13 obtained in 1995-1996), 33 strains from as ymptomatic children, obtained in similar periods and 30 strains from c hildren with bloody diarrhea, obtained in 1995-1996 were studied. Viru lence factors were investigated with a colony hybridization technique using probes that identify virulence genes. Serotypes were identified with commercial antisera. Results: Both SLTI and SLTII genes predomina ted in strains obtained from children with hemolytic uremic syndrome i n 1988-1989 and 1995-1996 and SLTI gene predominated in strains obtain ed in 1990-1933. Similar temporal variations in virulence genes of str ains obtained from asymptomatic children were observed. SLTI/SLTII pat tern predominated in strains obtained from children with bloody diarrh ea and the frequency of 0157 serogroup was lower, compared to strains obtained from children with hemolytic uremic syndrome. Conclusions: Th ere was a temporal variation in toxigenic genotypes of enterohemorrhag ic E. Coli strains, but no association between these genotypes and the risk for hemolytic uremic syndrome was observed.