Background: This study was a retrospective analysis of drug resistance mutations among HIV-1 strains prevalent in Silesia, Poland, from the origin of the epidemic to 2004. The investigations included both type and frequency of the reverse transcriptase inhibitors’ resistance mutations and estimation of the drugs’ resistance levels.
Material/Methods: Proviral DNA, obtained from peripheral blood mononuclear cells of the 101 HIV-1–infected patients, was amplified and sequenced in the pol gene fragment covering the first 256 codons of the reverse transcriptase (RT). Reverse transcriptase inhibitors resistance mutations were determined and interpreted with the HIVdb: Genotypic Resistance Interpretation Algorithm available from the Stanford University HIV Drug Resistance Database. In the examined population, 35 subjects (34.7%) received no antiretroviral treatment by the time of specimen collection.
Results: The overall frequency of the RT inhibitors resistance mutations in the studied population was 15.8%. Substitutions related to the reverse transcriptase inhibitors resistance were identified in 10 pol gene sequences (9.9%), all of them were present in the HIV-1 sequences obtained from persons receiving antiretroviral therapy.
Conclusions: Lack of drug-resistant viruses among treatment-naïve Silesian patients HIV-1-infected before the year 2004 may indicate that there was no transmission of the drug-resistant viruses in the studied population to that time.

Keywords: Poland, Mutation - genetics, HIV-1 - genetics, HIV Reverse Transcriptase - genetics, HIV Infections - virology, Genotype, Drug Resistance, Viral - genetics, Reverse Transcriptase Inhibitors - pharmacology, young adult