Prevalence of genotypic resistance to nucleoside analogues and protease inhibitors in Spain.

Objective To examine the prevalence of resistance mutations to nucleoside reverse transcriptase inhibitors (NRTI) and protease inhibitors (PI) in a representative HIV-1 population in Spain. Methods A cross-sectional study was conducted including 601 HIV-infected patients who attended 20 Spanish hospitals in June 1998. Drug resistant mutations were examined using hybridization line probe assays (LiPA). The 6 bp insert at position 69 and the codon 75 mutant were examined by sequencing analysis in specimens lacking reactivity to 69/70 and 74 bands on LiPA, respectively. Results Primary resistance to NRTI was recognized in nine out of 52 (17%) naive individuals, whereas primary resistance to PI was found in seven out of 126 (6%) PI-naive patients. The codons most frequently involved in NRTI resistance were at positions 70 (66%), 184 (44%), 215 (33%), and 41 (11%), whereas the most common PI resistance mutation was at codon 82 (6/7 subjects). In pre-treated patients, the overall prevalence of resistant genotypes was 72.9% for NRTI and 27.2% for PI. The most frequent NRTI mutations occurred at codons 184 (38.5%), 215 (30.1%), and 41 (22.5%), whereas the most frequent PI mutations in pre-treated subjects were found at positions 82 (15.8%) and 84 (11.4%). Overall, patients who began triple combinations as initial therapy showed a lower number of key resistance mutations than those who began highly active antiretroviral therapy (HAART) after being exposed to NRTI for a period of time (mean number of mutations, 0.1 versus 1.8, P  Conclusion The prevalence of primary genotypic resistance to NRTI and PI in Spain was 17% and 6%, respectively. Zidovudine, lamivudine, indinavir and ritonavir were the drugs most frequently affected. These data support the use of resistance testing prior to the introduction of first-line antiretroviral therapies in Spain. Among pre-treated subjects, drug resistance genotypes were less prevalent in those who began HAART as initial therapy.