Primary antiretroviral drug resistance among HIV type 1-infected individuals in Brazil.

Infection with drug-resistant human immunodeficiency virus type 1 (HIV-1) has been documented in all countries that have surveyed for it and may result in an unfavorable response to therapy. The prevalence and characteristics of individuals with transmitted resistance to antiretroviral drugs have been scarcely described in Brazil. We performed antiretroviral resistance testing prior to initiation of therapy in 400 subjects enrolled from 20 centers in 13 Brazilian cities between March and September 2007.