Ptomaine poisoning is an outdated term for food poisoning, dating from an era when illness after eating spoiled food was blamed on ptomaines, the nitrogenous compounds formed as bacteria decompose protein. Nineteenth-century chemists could isolate these substances from putrid meat and assumed they were the poisons at work. Bacteriology later showed the real causes: pathogenic organisms such as Salmonella and Staphylococcus aureus, and the powerful toxins some bacteria secrete into food. The phrase hung on in newspapers and household speech well into the twentieth century and is still occasionally used loosely to mean any stomach upset from bad food. Food scientists abandoned it decades ago, since it misidentifies both the agents and the mechanisms of genuine foodborne disease.