Multidrug resistant human immunodeficiency virus type I

Multidrug resistant (MDR) HIV, with reduced susceptibility to antiretroviral compounds from two or more classes of drugs, is now commonly found in treated patients. Several resistance pathways have been described for resistance to nucleoside analogue reverse transcriptase (RT) inhibitors (NRTI). Large crossresistance patterns are known for non-nucleoside RT inhibitors (NNRTI) and protease inhibitors (PI). Despite an initial and transient decrease in viral fitness, MDR virus can conserve excellent in vitro and in vivo replication capacities due to the accumulation of compensatory mutations. MDR virus has been transmitted from person-to-person, raising serious clinical and public health concerns. Treatment strategies for MDR virus are still not clearly defined, and treatment options are currently limited. However, a better use of antiretroviral drugs in conjunction with resistance testing and drug level monitoring may result in a prevention of the emergence of new MDR virus.