text: what is the lethal dose for e.coli?   contrary to popular belief, escheria coli is totally harmless to humans.  it is only the agressive mutant e. coli 0157 that is deadly.  the amount required to kill someone varies totally.  remember "there are no absolutes in a biological system".  a child, a pensioner or a person who is immunocompromised will die when subjected to a much smaller dose than a healthy 20-something male