Salmonella typhimurium bacterium, coloured scanning electron micrograph (SEM). This bacterium is also known as Salmonella enterica serovar typhimurium. It is a Gram-negative, rod-shaped bacterium that has flagella (hair-like structures, purple), which it uses for locomotion. S. typhimurium is a major cause of food poisoning (salmonellosis) in humans. Salmonellosis is most commonly caught from infected pork, poultry and eggs. It may also be spread by household pets. Symptoms include fever, chills, severe diarrhoea and vomiting. It may be fatal in the very young, the elderly and individuals with reduced immune systems. Treatment is with antibiotics.