Prevalence of genotypic resistance to nucleoside analogues in antiretroviral-naive and antiretroviral-experienced HIV-infected patients in Spain

Objective: To determine the prevalence of genotypic resistance to nucleoside analogues (NA) in a large group of HIV-infected individuals in Spain, some of whom had no previous treatment with antiretroviral drugs (antiretroviral-naive) and some of whom had such experience (antiretroviral-experienced). Setting: Cross-sectional study in outpatient clinics in three reference hospitals for HIV/AIDS located in Barcelona, Madrid and Seville, Spain. Patients and methods: Primary mutant genotypes were examined in plasma HIV RNA collected from 150 antiretroviral-naive subjects, half in 1993 and the other half in 1997. Furthermore, drug resistance mutations were analysed in plasma collected from another 150 antiretroviral-experienced patients who had received 2 NA for longer than 1 year, either in sequence as monotherapy or as combination therapy. A line probe assay was used for recognizing mutations conferring resistance to zidovudine (ZDV), didanosine (ddI), zalcitabine (ddC), and lamivudine (3TC). A point-mutation nested-PCR assay was used for examining a codon 151 mutation associated with multiple drug resistance. Results: One or more mutations associated with primary resistance to NA were seen in 10 antiretroviral-naive (13.3%) patients in 1993 and in nine (12%) in 1997. In all but two cases, they were associated with ZDV resistance. In contrast, all but six (96%) of the antiretroviral-experienced subjects harboured drug-resistant mutant viruses. The codon 184 mutation (associated with resistance to 3TC) was detected in 92% of patients treated with 3TC, but also in 18% of those treated with only ddI or ddC. The codon 215 mutation was found in 67.3% of patients who had been exposed to ZDV; the codon 69 mutation was found in 15% of patients treated with ddC; and the codon 74 mutation was found in only 7.2% of patients treated with ddI. Finally, the codon 151 multidrug resistant mutation was found in four (2.7%) of 150 patients with a longterm exposure to NA. Conclusions: Overall, the prevalence of drug-resistant HIV-1 genotypes was 12.7% in antiretroviral-naive patients, most of whom had ZDV-resistant mutants. There is no evidence of an increase during the last 5 years. However, multidrug-resistant HIV genotypes are currently circulating in Spain.