1. High prevalence of antiretroviral drug resistance among HIV-infected pregnant women in Buenos Aires, Argentina Zapiola 1, D.M. Cecchini 2, S. Fernandez Giuliano 1, M. Martinez 2, C.G. Rodriguez 2, M.B. Bouzas 1. 1 Hospital Muñiz, Virology Unit, Buenos Aires, Argentina, 2 Hospital Cosme Argerich, Working Group in Prevention of Mother-to-Child Transmission, Buenos Aires, Argentina Background & Objective: The presence of primary mutations in the viral genome is a major cause of drug resistance. Monitoring the presence of drug resistance-associated mutations (RAMs) in HIV-infected pregnant women (HPW) is crucial for optimizing antiretroviral therapy (ART) selection. Until recently, genotypic resistance tests were not routinely available for HPW in Argentina and information about the prevalence of RAMs in this population is limited. We aimed to determine trends in the prevalence of RAMs in HPW assisted at a public hospital in Buenos Aires city (Hospital Argerich, located in La Boca commune, limiting Buenos Aires province). Methods: Prospective sentinel epidemiological survey. Baseline plasma samples were sequenced using TRUGENE TM HIV-1 Genotyping Kit at a reference laboratory (Hospital Muñiz, Virology Unit). RAMs were identified in ART-naïve (WHO guidelines) and ART-experienced patients (IAS-USA mutation list). RAMs prevalence was compared for two periods: 2008-2011 vs. 2012-2014. AIDS 2016 #TUPDB0102

2. Results I 136 HPW were included: 77 (56.6%) naïve and 59 (43.4%) ART-experienced (24 with ongoing ART and 35 with a history of exposure to ART). A total of 37 (27.2%) women had at least one RAM: 25/94 (26.5%) in 2008-2011 and 12/42 (28.5%) in 2012-2014 (p>0.05). Naïve HPW: transmitted resistance was observed mainly for non-nucleoside reverse transcriptase inhibitors (NNRTIs): 14.3% in 2008-2011 and 17.8% in 2012-2014 (p>0.05), being K103N the most common mutation: 12.2% in 2008-2011 and 10.7% in 2012-2014 (p>0.05).

3. Results II Among the ART-experienced HPW, 37.3% had RAMs: 33.3% in 2008-2011 and 50% in 2012-2014 (p>0.05): In those with ongoing ART subgroup, 50% had nucleoside reverse transcriptase inhibitors-RAMs and 45.8% had NNRTI-RAMs. In those with a history of (but not ongoing) ART-exposure, 17.1% had NNRTI- RAMs. Predominant RAMs in experienced HPW were K103N (20,3%), M184V (11,8%) in RT gene and L90M (11,8%) in PR gene.  Conclusions:  This sentinel study demonstrates an overall high prevalence of RAMs in HPW in Buenos Aires city, which remained stable over the two periods analyzed.  Considering the >15% prevalence found in naïve HPW is above the threshold suggested by WHO for routine resistance surveillance in a certain population, access to genotypic tests should be warranted.  The moderate to high levels of NNRTI resistance observed, prevents empirical prescription of EFV or NVP-based ART in this population. Thank you !!!