A new study showed that HIV-infected individuals had very high levels of harmful bacteria in their digestive systems that could make their lack of immunity even worse. The researchers believed that the bacteria might directly weaken the digestive system's barriers and specific immunity.
Researchers studied 32 men, including nine without HIV infection and 23 with HIV infection. They found that the bacteria in the digestive tracts of HIV-infected individuals differed from the bacteria found in digestive tracts of HIV-uninfected persons. The HIV-infected participants had unusually high levels of salmonella, escherichia, shigella, and staphylococcus bacteria in their digestive tracts. These bacteria cause food poisoning that would not be serious for a person with an intact immune system, but in HIV-positive persons, the symptoms of food poisoning -- fever, diarrhea, abdominal pain, and dehydration -- persist, causing the body to waste away from the infection.
The researchers suggested that high levels of harmful bacteria in the digestive tract were part of the way HIV attacked the patient's immune system to make it useless. The existence of a large amount of bacteria in the body would trigger the body's initial immune response, called inflammation, and summon other immune cells to the infection site to kill the invading bacteria. HIV multiplies by entering immune response cells that would normally stop an infection and destroying them. The inflammation then continues in the body, making it vulnerable to even more infections. Since the researchers have identified high levels of harmful bacteria in HIV-infected patients, clinicians treating HIV-infected individuals can pay attention to symptoms of infection from these bacteria.
The full report, "Dysbiosis of the Gut Microbiota Is Associated With HIV Disease Progression and Tryptophan Catabolism," was published online in the journal Science Translational Medicine (2013; doi:10.1126/scitranslmed.3006438).