Background:  HIV treatment guidelines have evolved over the last few years shifting from more aggressive to more conservative approaches. Monitoring newly infected patients for HIV drug resistance is important for first-line treatment decisions as well as for public health considerations.

Methods:  The proportion of genotypic drug resistance was examined in 118 consecutive newly HIV-infected individuals seen since January 1997 to September 2003 in 4 different hospitals distributed across Spain. Only major drug resistance mutations (latest IAS-USA Panel list) at the RT and protease were considered for this analysis. During the same period, the proportion of patients with chronic HIV infection and HIV-RNA <50 copies/mL was examined, in order to determine the extent and effectiveness of antiretroviral therapy.

Results:  A total of 118 recent HIV-seroconverters have been identified. Mean time of infection was 8 months and 73% were infected through homosexual contact. The rate of primary drug resistance mutations was 33.3% (1997), 29.4% (1998), 20% (1999), 14.3% (2000), 4.2% (2001), 26.1% (2002), and 7.7% (2003). On the other hand, the proportion of patients with undetectable viremia was 44.6% (1997), 46.1% (1998) 37.4% (1999), 47.5% (2000), 52.9% (2001), 39.7% (2002) and 58.1% (2003). An inverse correlation between yearly rates of subjects with undetectable VL and drug-resistant transmitted viruses was found (Spearman’s r = -0.643, p = 0,06). The lowest rate of drug resistance transmission corresponded to the highest proportion of undetectable viremia in 2001, when treatment guidelines in use were more aggressive. In 2002 the rebound in transmission of drug-resistant viruses was accompanied with a reduction of subjects with undetectable viremia, perhaps reflecting a widespread use of drug holidays or structured treatment interruption. In 2003, a new decrease on the rate of transmission of drug-resistant viruses and an increase in the proportion of patients with undetectable viremia was seen, which is in agreement with the restricted use of treatment only for patients with <350 CD4⁺ cells/mL.

Conclusions:  The rate of primary drug resistance in recent HIV-seroconverters seems to reflects indirectly (“mirror image”) the proportion of individuals with undetectable viremia, following antiretroviral treatment rules at any given time point.

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Keywords: HIV-seroconvertoters; drug resistance; antiretroviral therapy