7th Conference - Abstract 496

Prevalence of Drug-Resistant HIV-1 in Patients Who Are the Source of Occupational Exposures to Health Care Workers

R. CHEINGSONG*, E. BELTRAMI, R. RESPESS, D. CARDO, and the Occupational HIV Exposure Study Group. CDC, Atlanta, GA

Post-exposure prophylaxis (PEP) with zidovudine (ZDV) and lamivudine (3TC) is currently recommended for certain occupational HIV exposures. Addition of a protease inhibitor (PI) is recommended for exposures that pose an increased risk for HIV transmission or where resistance to antiretroviral agents is known or suspected. Although antiretroviral therapy among persons with HIV has become widely implemented, the spectrum of HIV drug resistance among patients who are the source for occupational exposures to HIV-1 needs further studied. By sequencing, we assessed the prevalence of resistance-associated mutations in 42 HIV-1 infected source patients enrolled at 7 sites in the US between 1998-1999. Of these patients, 20 were drug naïve and 22 were drug experienced. Overall, the prevalence of primary mutations associated with resistance to RT inhibitors (RTIs) or PI was high (16/42, 38%). ZDV- and/or 3TC-associated mutations were common (14/16, 88%). Single mutations associated with resistance to 3TC (M184V) were observed in five patients. Two patients had mutations associated with either non-nucleoside RTI (K103N) or PI (L90M) resistance. Nine patients had two or more mutations associated with RTI and/or PI resistance. Seven samples with two or more mutations were phenotyped by recombinant virus assays. Six of them had phenotypic resistance that supported the genotypic analysis. No HIV seroconversions were observed among exposed health care workers. Although the results demonstrate a high proportion of HIV-1 drug resistant strains in the source patients, in particular those who were on therapy, the significance of the emergence of drug resistant HIV-1 strains and the implications for PEP are uncertain.

Key Words: drug resistance, occupational exposur, prophylaxis