This page discusses Escherichia coli (E. coli), a bacterium primarily found in humans and animals. While most strains are harmless, certain pathogenic strains like O157:H7 cause illnesses and are asso...This page discusses Escherichia coli (E. coli), a bacterium primarily found in humans and animals. While most strains are harmless, certain pathogenic strains like O157:H7 cause illnesses and are associated with foodborne outbreaks. E. coli is also important in genetic engineering for drug production, although there are concerns about engineered strains affecting humans.