| Enterohemorrhagic Escherichia coli (EHEC) strains, most notably E. coli O157:H7, are the primary cause of hemorrhagic colitis and hemolytic uremic syndrome (HUS). Approximately 8% of cases of EHEC-associated childhood diarrhea progress to HUS. Since HUS is a heterogeneous syndrome, the initial diagnosis is often difficult and only the development of systemic symptoms guides the diagnosis. Pathogenesis is poorly understood and it has not been possible to predict the onset of this post-diarrheal syndrome. Both basic research and clinical case management would benefit from determination of EHEC features associated with HUS potential.;This research project was an interdisciplinary collaborative effort to examine various isolates of enterohemorrhagic E. coli for differences in pathogenicity. Preliminary in vitro studies suggested a correlation between genomic restriction pattern and HUS phenotype in isolates of E. coli O157:H7, the serotype most commonly associated with the development of HUS. We tested the validity of O157:H7 isolate association with HUS, according to genomic restriction pattern as well as other parameters. Data collected from in vitro studies was also used to train an artificial neural network (ANN) to recognize the patterns most highly associated with increased pathogenicity. Toxin expression in vivo has a direct impact on the severity of kidney complications as well as damage to other organs.;A factor that appeared to influence pathogenicity was an increased expression of the Shiga toxins in the highly pathogenic strains as measured by a Vero cell cytotoxicity assay. Quantitative measurements of toxin production in fifty clinical E. coli isolates were compared statistically with known patient outcome data. The resulting data suggested a relationship between the level of cytotoxic activity of individual isolates and an increased likelihood of the development of HUS, although the data failed to reach a level of statistical significance. Modifications to the cytotoxicity assay may increase its accuracy and repeatability as a measurement of pathogenic potential. Central hypothesis---A battery of selected parameters, including restriction patterns, biochemical analyses and measures of toxin potency (individually or in combination) can serve to predict the pathogenic potential of particular enterohemorrhagic E. coli for humans. |
