Typhoid fever, also known as Salmonella typhi or commonly just typhoid is a common worldwide illness, transmitted by the ingestion of food or water contaminated with the feces of an infected person. The bacteria then perforate through the intestinal wall and are phagocytosed by macrophages. It is caused by the bacterium Salmonella typhi  The organism is a Gram-negative short bacillus that is motile due to its peritrichous flagella. The bacterium grows best at 37 °C/99 °F – human body temperature.