Immune response to Escherichia coli O157:H7 in hemolytic uremic syndrome following salmonellosis

Abstract.

Escherichia coli O157:H7, a Shiga-like toxin (SLT)-producing enteric pathogen, has been implicated in most cases of post-diarrheal hemolytic uremic syndrome (D+HUS). Infection with other bacterial pathogens such as Salmonella has also preceded D+HUS episodes, leading to speculation that these organisms may also be etiological. We present two children with unrelated D+HUS following salmonellosis. Both children had negative stool cultures on sorbitol-MacConkey agar soon after the onset of diarrhea. After the diagnosis of HUS, both patients had repeat stool cultures positive for Salmonella alone. Polymerase chain reactions for SLT I and II gene sequences in Salmonella isolates were negative. Enzyme-linked imunosorbent assay for specific humoral response to E. coli O157:H7 lipopolysaccharide in acute and convalescent serum samples revealed evidence of heretofore undetected E. coli O157:H7 infection contemporaneous with each D+HUS episode. These cases demonstrate that isolation of only non-SLT-producing microbes from children with D+HUS should raise suspicion of concurrent undetected infection with SLT-producing organisms. Assaying specific immune response to E. coli O157:H7 can be an important epidemiological adjunct. Bacterial infection with non-SLT-producing Salmonella may represent concomitant enteric pathology rather than D+HUS-instigating infection.