Enterobacteriaceae v The enterobacteriaceae are a large and diverse family of Gram-negative rods, members of which are both free-living and part of the indigenous flora of humans and animals v Some of these organisms are part of the normal intestinal flora, eg.E coli y while others are regularly pathogenic for humans and animals: Salmonella, Shigella The enterobacteriaceae are a large and diverse family of Gram-negative rods, members of which are both free-living and part of the indigenous flora of humans and animals  Some of these organisms are part of the normal intestinal flora, eg.E.coli  while others are regularly pathogenic for humans and animals: Salmonella, Shigella Enterobacteriaceae