In advanced HIV infection, the homeostatic balance between gastrointestinal indigenous bacteria and gut immunity fails and microbes are able to overcome the intestinal barrier and gain the systemic circulation. Because microbial translocation is not fully controlled by antiviral therapy and is associated with inefficient CD4+ reconstitution, we investigated the profile of translocating bacteria in peripheral blood of 44 HIV-infected patients starting therapy with advanced CD4+ T-lymphopenia and displaying poor CD4+ recovery on virologically suppressive HAART. According to CD4+ reconstitution at 12-months HAART, patients were considered Partial Immunological Responders, PIRs (CD4+=250/µl, n?=?29) and Immunological non Responders, INRs (CD4+