Exactly because it is a nutritious material, meat is especially vulnerable to colonization by microbes, mainly bacteria. And because animal skins and digestive tracts are rich reservoirs of bacteria, it’s inevitable that initially clean meat surfaces will be contaminated during slaughter and the removal of skin, feathers, and innards. The problem is magnified in standard mechanized operations, where carcasses are handled less carefully than they would be by skilled butchers, and where a single infected carcass is more likely to contaminate others. Most bacteria are harmless and simply spoil the meat by consuming its nutrients and eventually generating unpleasant smells and a slimy surface. A number, however, can invade the cells of our digestive system, and produce toxins to destroy the host cells and defenses and to speed their getaway from the body. The two most prominent causes of serious meat-borne illness are Salmonella and E. coli.