Salmonella 5. Salmonella organisms is acid-sensitive with 104 to 108 organisms required for infection risk factors for disease include a)antacid use b)prior antibiotics(reduces competition by normal flora), and c) depressed immune function(AIDS and transplant patients, sickle cell disease)Salmonella 5. Salmonella organisms is acid-sensitive, with 104 to 108 organisms required for infection. Risk factors for disease include a) antacid use, b) prior antibiotics (reduces competition by normal flora), and c) depressed immune function (AIDS and transplant patients, sickle cell disease). 13