Salmonellosis Salmonellosis is a bacterial 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.at scratch disease is a bacterial disease caused by Bartonella henselae. Young cats and kittens are most likely to be the source of human infection. The infection, which does not cause disease in cats, is transmitted between cats by fleas.