A recent UCLA study led by Dr. Jennifer Fulcher of the DGSOM Division of Infectious Diseases and in collaboration with UCLA CBAM researchers suggest certain gut bacteria could contribute to one’s risk for HIV infection. A link between chronic HIV and changes in gut bacteria is known, however, further research is needed to understand if and how these bacteria could affect HIV transition. In this study, microbiome gut samples of 27 men who have sex with men and who were positive for HIV were examined and compared to samples of 28 men who were at similar behavioral risk for infection but did not have HIV. Researchers found there was very little change in the HIV positive men’s gut bacteria during the first year. They did, however, find that the men who had acquired HIV had pre-existing differences in gut bacteria even before they became infected, compared with those who did not have HIV. Compared with uninfected at-risk controls, the men who had acquired HIV had decreased levels of Bacteroides species (a type of bacteria found in the lower intestinal tract and key in maintaining a healthy gut environment) and increased levels of Megasphaera elsdenii (a bacteria whose role is not yet entirely known). Researchers also found that prior to infection, those who had acquired HIV had elevated inflammatory cytokines and bioactive lipids, both of which are associated with systemic inflammation. These findings highlight the importance of understanding the role of the microbiome in HIV susceptibility.