Evidence of tenofovir resistance in chronic hepatitis B virus (HBV) infection: an observational case series of South African adults por Mokaya, J, Maponga, TG, McNaughton, AL, Van Schalkwyk, M, Hugo, S, Singer, JB, Sreenu, VB, Bonsall, D, de Cesare, M, Andersson, M, Gabriel, S, Taljaard, J, Barnes, E, Preiser, W, Van Rensburg, C, Matthews, PC