Surface structures of Escherichia coli that produce diarrhea by a variety of enteropathic mechanisms.

Strains of Escherichia coli, mostly of human origin, were obtained from several different investigators who had isolated them from patients with diarrhea from many different parts of the world. The mechanisms by which these E. coli were thought to have caused diarrhea included: (i) synthesis of labile, stable, or Shigella dysenteriae-like enterotoxins; (ii) invasion of the intestinal mucosa; and (iii) unknown. Each strain was carefully examined for pili or flagella to correlate the presence or absence of such surface structures with a particular mechanism of diarrhea. The presence of pili was determined by colony morphology on minimal media, pellicle formation in static broth culture, and transmission electron microscopy. The pili were categorized as type 1 if the bacteria fermented rhamnose and if pellicle formation was inhibited by alpha-methyl-d-mannoside. The presence of flagella was confirmed in motility media and by transmission electron microscopy. Six invasive E. coli strains lacked pili and flagella. Ten E. coli strains that synthesized enterotoxins or produced diarrhea by an unknown mechanism were piliated (seven with type 1 pili), and all but one had flagella. Pili and flagella seem to be associated with strains of E. coli that produce diarrhea by enterotoxin synthesis or unknown mechanisms. Strains that produce diarrhea by mucosal invasion lack both types of surface structures.