Salmonellosis - Aquariums Salmonellosis is a infection of the intestines caused by a group of bacteria called Salmonella. The bacteria are shed in the stool of infected animals and humans. Infection can happen when a person eats food or drinks water or milk that has been contaminated with Salmonella bacteria. Salmonella bacteria have also been found in tropical fish and home aquariums. Infection with salmonella can cause serious disease especially in children younger than 5 years of age, the elderly, and persons with weakened immune systems.