Escherichia coli O157:H7 infections: discordance between filterable fecal shiga toxin and disease outcome.

Shiga toxin (Stx)-producing Escherichia coli O157:H7 are the most common cause of hemolytic uremic syndrome (HUS). We detected free fecal Stx in 48%, 40%, and 17% of infected children with uncomplicated diarrhea, children who subsequently developed HUS, and children with HUS, respectively. Vero cell assay detected Stx more frequently than did a commercial Stx enzyme immunoassay. In children's stool samples obtained on or before day 4 of illness, each 10-fold decrease in titer was, paradoxically, associated with 3.8-fold increased odds of developing HUS (P=.03; 95% confidence interval, 0.77-19.7). The fecal Stx type did not correlate with the Stx expressed by bacteria grown in vitro and was not related to bacterial titer in the studied samples. These data suggest that therapeutic and diagnostic strategies directed toward binding or identifying intraintestinal fecal Stx may have limited success.