Salmonella bacteria. Coloured scanning electron micrograph (SEM) of Salmonella paratyphi bacteria. These bacteria, also known as Salmonella enterica enterica, are Gram-negative, rod-shaped cells. Salmonella is a major cause of food poisoning (salmonellosis) in humans, most commonly caught from infected pork, poultry and eggs. Symptoms include fever, chills, severe diarrhoea and vomiting. Treatment is with antibiotics.