Folks in the popular media don’t seem to know, or care, that the often fatal E. coli (E. coli 0157:H7) causing the current outbreak of hemorrhagic diarrhea, sometimes complicated by hemolytic uremic syndrome, is completely different from the ubiquitous E. coli that inhabits the colon of each of us and commonly causes infection when it winds up someplace is shouldn’t (urinary tract or bloodstream).
If you don’t think this is confusing to people try telling your patient (when 0157:H7 is hot news) with a mild UTI “Oh, it’s just E. coli” and note the reaction. This pathogen should be referred to in media reports as “E. coli 0157:H7”, not “E. coli.”
The ubiquitous form of E. coli is not an intestinal pathogen. Six less common forms do not normally inhabit the human GI tract and are in fact enteric pathogens. These latter forms have little in common except for a propensity to cause intestinal disease, with distinctly different pathogenic mechanisms. Only one of these six forms, enterohemorrhagic E. coli, causes extraintestinal disease (hemolytic uremic syndrome). These are principally of the 0157:H7 variety, the subject of the current news stories.
The only other one of the six forms of enterovirulent E. coli of importance in the developed world is enterotoxigenic E. coli, believed to be the principal etiologic agent of traveler’s diarrhea. The toxin elaborated by this organism increases the production of cyclic AMP and GMP resulting in a secretory (non-inflammatory) diarrhea.
The other forms of enterovirulent E.coli are enteropathogenic E. coli, enteroinvasive E. coli, enteroaggregative E. coli and diffusely adherent E. coli.