Update on emergence of HIV-1 resistance to antiretroviral drug classes in an Italian national database: 2007-2009.

We analysed trends of human immunodeficiency virus type 1 (HIV-1) drug resistance during 2007-2009 in the Italian national HIV drug resistance database 'ARCA'. Prevalence of resistance in each year was examined on the basis of the presence of major International AIDS Society-2009 mutations. Predictors of resistance were analysed by multivariable logistic regression. Nine hundred and sixty-six patients were selected. Resistance to nucleoside reverse transcriptase inhibitors and protease inhibitors showed a significant decline with respect to previous surveys. Resistance to any class of drug and three drug classes remained stable. Independent predictors of three-class resistance were the number of treatment regimens experienced, prior suboptimal nucleoside reverse transcriptase inhibitor therapy and the current use of ritonavir-boosted protease inhibitors.