Drug-resistance surveillance among newly HIV-1 diagnosed individuals in Buenos Aires, Argentina.

Objective: Our objective was to estimate primary resistance in an urban setting in a developing country with a long history of antiretroviral delivery and high coverage levels.
Design: We carried out a resistance surveillance study according to WHO HIV-Resistance Guidelines.
Methods: Blood samples were collected from 323 drug-naive HIV-1 infected individuals diagnosed at two HIV voluntary counselling and testing centers in Buenos Aires. Viral-load, CD4 cell counts and detuned assays were performed on all samples. The pol gene was sequenced and the resistance profile determined. Phylogenetic analysis was performed by neighbor-joining trees and bootscanning analysis.
Results: We found that 12 (4.2%) of the 284 samples sequenced harbored primary resistance mutations, of which K103N, M41L and V108I were most prevalent. Phylogenetic analysis revealed evidence for the transmission of the K103N mutation among the drug-naive population. The proportion of recent infections identified by the detuned assay was 10.1%.
Conclusions: Levels of primary resistance in Buenos Aires are still low, despite a long history of ARV delivery and high coverage levels.