Background:Resistance to antiretroviral (ARV) drugs represents a major obstacle to the success of HIV therapy. The aim of the study was to examine the prevalence of genotypic resistance to ARV drugs in a large group of HIV-infected individuals incarcerated in penal facilities.Material/Methods:We analyzed the reverse transcriptase and protease genes on plasma samples collected from 309 HIV-infected prison inmates in Madrid. In order to compare the prevalence of resistance at different periods and detect any trend over time, half of the samples from ARV-naive and half from pre-treated subjects were randomly collected in 1999 and in 2001.Results:Overall, 63.7% of specimens harbored plasma HIV-RNA above 1000 copies/ml. Genotypic data were obtained in 94.4% of them. Primary resistance mutations among 127 drug-naive subjects were recognized in 13% in 1999 vs. 15% in 2001. In contrast, drug resistance was found in 35% and 59% of 182 pre-treated subjects in 1999 and 2001.Conclusions:Drug resistance has increased over the last two years among inmates on ARV drugs and currently affects 59% of those failing treatment. A nearly 3-fold increase has been noticed for NNRTI resistance. In comparison with HIV-positive subjects outside jail on ARV drugs, prisoners are more likely to experience virological failure, but show a lower rate of drug resistance; this affects particularly drugs with a low genetic barrier (i.e. NNRTI and 3TC).

Keywords: Anti-HIV Agents - therapeutic use, Drug Resistance, Viral, Endopeptidases - blood, HIV - drug effects, HIV - genetics, HIV Infections - drug therapy, Mutation, Prisoners, RNA, Viral - blood, RNA, Viral - isolation & purification, RNA-Directed DNA Polymerase - blood, Spain, Viral Load