Three of the most common bacterial causes of diarrhea in HIV-positive people are organisms belonging to the Salmonella, Campylobacter, and Shigella families.
Salmonellosis is the name of the disease caused by Salmonella infection. Studies have demonstrated that HIV-positive people are at a higher risk for salmonellosis, between 20 to 100 times more so than HIV-negative people. Salmonella can enter the body by eating or drinking contaminated food or water or by contact with infected people or animals. The most common sources of Salmonella include contaminated raw poultry, eggs, and unpasteurized milk and cheese products. Other sources of exposure include contact with infected animals, especially turtles, iguanas, other reptiles, chickens, cattle and poultry.
Campylobacteriosis is caused by the Campylobacter organism, most notably Campylobacter jejuni. It has been documented in cattle (beef), chickens, birds, and flies. It is sometimes present in non-chlorinated water sources, such as streams and ponds. Oral-anal sex is believed to be another route of Campylobacter transmission. According to the U.S. Food and Drug Administration, Campylobacter jejuni is the leading cause of bacterial diarrhea in the United States. HIV-positive people, particularly men who have sex with men, are 39-times more likely to be infected with Campylobacter jejuni than HIV-negative people.
Shigellosis is caused by the Shigella organism. There are several kinds of Shigella bacteria. Shigella sonnei, also known as "Group D" Shigella, accounts for over two-thirds of the shigellosis in the United States. A second type, Shigella flexneri, or "Group B" Shigella, accounts for almost all of the rest. Shigella is most commonly spread from one person to another, through direct contact with feces. Shigella infection is more common among HIV-positive people and can lead to either mild or severe cases of shigellosis.
In HIV-positive people with suppressed immune systems, salmonellosis, campylobacteriosis, and shigellosis can lead to severe diarrhea. These infections, especially salmonellosis, can also spread from the intestines to the blood stream and then to other body sites. This can cause death unless the person is treated quickly.