Transmission of drug-resistant HIV-1 in Europe remains limited to single classes

Background: The spread of drug-resistant HIV-1 might compromise the future successof current first-line regimens.Objective: To analyse the extent and impact of transmission of drug-resistant HIV-1variants in Europe.Design and methods: The European prospective programme (SPREAD) collecteddemographic, clinical and virological data from 1245 HIV-1-infected individuals in17 countries diagnosed in 2002–2003. The potential impact of transmitted drugresistance mutations (TDRMs) on therapy response was determined by using genotypicinterpretation algorithms.Results: The overall prevalence of viruses with drug-resistance mutations was 9.1%[96/1050; 95% confidence interval: 7.5–11.1]. The majority (71%) harboured only asingle amino acid substitution with limited effect on predicted drug susceptibility.Mutationsassociatedwithresistancetonucleosidereversetranscriptaseinhibitorswereobserved most frequently [57/1050 (5.4%)], followed by mutations related to proteaseinhibitors [32/1050 (3.0%)] and mutations related to non-nucleoside reverse transcrip-tase inhibitors (NNRTIs) [27/1050 (2.6%)].In some cases, however, resistance was quite extensive. Four individuals were infectedwith viruses with reduced susceptibility to all nucleoside reverse transcriptase inhibi-tors, 3 to all protease inhibitors and 20 to both NNRTIs. Remarkably, in one individual,the resistance pattern was so extensive that none of the available current antiretroviraldrugs was predicted to be fully active.Conclusion: The prevalence of TDRM-HIV is quite prominent (9.1%) but did notincrease in comparison with a large retrospective European study. Particularly thepresence of single NNRTI mutations may impact the efficacy of the first-line regimens.Continuous prospective monitoring remains indicated to explore the patterns andfactors contributing to the transmission of TDRMs as well as the potential clinicalconsequences.