Genotypic resistance mutations in treatment-naïve and treatment-experienced patients under widespread use of antiretroviral drugs in Thailand: implications for further epidemiologic surveillance.

The aims of this study were to illustrate the prevalence and determinants of mutations associated with antiretroviral drug resistance in a group of antiretroviral-naive and treatment-experienced patients in Thailand, where antiretroviral drugs are widely used. One hundred and thirteen treatment-naive (92 CRF01_AE and 21 subtype B patients) and 1,709 treatment-experienced patients were recruited. Genotypic resistance to antiretroviral drugs was studied by sequencing the isolated viruses. Mutation frequencies in treatment-naive patients were reported along with those for treatment-experienced patients. The results showed that all of the patients with treatment-experienced patients showed the same pattern of genotypic resistance. The results also showed that only 14 drug-naive patients (12.4%) carried HIV-1, with at least one drug-resistant mutation. Moreover, four drug-naive patients were found to carry the marker mutations for transmission of drug resistance. The most commonly found marker in drug-naive patients was M36I/V/L (n=90, 81.1%), which is a common natural polymorphism among HIV-1 subtype CRF01_AE individuals. In order to prevent the rapid emergence of resistant virus strains, a national program to monitor antiretroviral drug resistance should be established. We also recommend routine genotypic testing in treatment-naive patients before starting antiretroviral therapy to prevent subtherapeutic response and viral failure.