Platelet-activating factor and Escherichia coli O157:H7 infections

Abstract.

The role of platelet-activating factor (PAF), a phospholipid inflammatory mediator, in Escherichia coli O157:H7-associated hemolytic uremic syndrome (HUS) is unknown. PAF is synthesized by diverse cells and is degraded by PAF-acetylhydrolase (PAF-AH). Deficient PAF-AH activity results from a G→T transversion at position 994 of exon 9. We examined children infected with E. coli O157:H7 to determine if PAF levels or the PAF-AH (G994T) mutation reflects the risk of developing HUS. Plasma PAF concentrations were determined using chloroform/methanol extraction, thin layer chromatography purification, and scintillation proximity assay in 10 patients with uncomplicated infection (UI), 10 infected patients who subsequently developed HUS (pre-HUS), 5 HUS patients, and 8 healthy controls. The PAF-AH (G994T) allele frequency was determined in 52 UI children, 15 with HUS, and 11 controls. Wilcoxon rank sum tests were performed to test differences in location (median) of pairs of groups. PAF levels were higher in the UI (P=0.04) and pre-HUS (P=0.01) groups than in healthy controls. No subject had the PAF-AH (G994T) allele. Thus, elevated plasma PAF levels occur in E. coli O157:H7-infected children, even without HUS, but diminish when HUS develops. The PAF-AH (G994T) allele does not contribute to the risk of developing HUS.