| Abstract: | First described in 1885, Escherichia coli gradually emerged as a cause of infantile diarrhea. Currently, four pathogenic categories of diarrheagenic E. coli are recognized: enteropathogenic (EPEC), enterotoxigenic (ETEC), enteroinvasive (EIEC), and enterohemorrhagic (EHEC). Of these, ETEC and EPEC are important causes of pediatric diarrhea, especially in developing countries. ETEC strains are characterized by their production of well-defined heat-labile or heat-stable enterotoxins. In the absence of other identifying characteristics, EPEC strains have been identified by serotyping only; recent laboratory and clinical investigations have shown that these strains constitute a distinctive group of pathogenic microorganisms displaying characteristic adherence to cultured epithelial cells and producing pathognomonic histopathologic changes in experimentally infected animals and naturally infected children. The pathogenicity of most strains of EPEC is associated with the carriage of a 55- to 70-megadalton plasmid that specifies the production of an adherence factor. EPEC strains may also owe their pathogenicity to the production of at least one enterotoxin, possibly a Shiga-like cytotoxin. |
