Salmonella infection, or salmonellosis, is a bacterial disease of the intestinal tract. Salmonella is a group of bacteria that cause typhoid fever, food poisoning, gastroenteritis, enteric fever and other illnesses. People become infected mostly through contaminated water or foods, especially meat, poultry and eggs.Salmonella is a gram-negative, rod-shaped bacilli that can cause diarrheal illness in humans. Put simply-Salmonella is a bacterium shaped like a rod with a cell wall composed of peptidoglycan.eople become infected mostly through contaminated water or foods, especially meat, poultry and eggs. Salmonella is a gram-negative, rod-shaped bacilli that can cause diarrheal illness in humans. Put simply-Salmonella is a bacterium shaped like a rod with a cell wall composed of peptidoglycan.