Ptomaine, TOH mayn, poisoning is an outdated term for a type of food poisoning. Ptomaines are nitrogen-containing compounds that are formed by the bacterial decomposition of proteins. Although ptomaines are present in spoiled foods, the human digestive system can completely neutralize them. It is the bacteria--or the toxins (poisons) that are produced by the bacteria--that actually cause "ptomaine" poisoning. Ptomaines are now classified in a group of chemicals that do not cause food poisoning. See also Food poisoning.