Background:  While <0.06% of the general Israeli population are infected with HIV, the prevalence is much higher among particular groups. These groups can be clearly distinguished demographically by risk behavior category and by virus subtype. We investigated drug resistance transmission rates in Israel within the different groups.

Methods:  Plasma samples of newly diagnosed patients were collected between June 1999 and June 2003. Baseline sequences of viral protease and RT genes from 170 drug-naïve patients (>15% of all cases diagnosed) were determined. Sequences were subtyped by reference to the Stanford database. Statistical analysis was performed using chi-square test.

Results:  Samples consisted of 29 subtype B, 100 C, and 41 others (18 A, 16 AE, 2 AC, and 5 F; collectively:  A group). Major drug resistant mutations (Pr:  L90M; RT: M41L, K103N, V106M, M184V, G190A, L210W, T215Y/F, or K219R) were detected in 3 B, 6 C, and 1 A subjects. In addition, 14 patients, 3 B and 11 C, had secondary mutations (Pr: M46I; RT: A98G, V108I, or Y181S). Although resistance to all 3 antiretroviral drug classes was found, only one patient had multi-class resistance. Among subjects infected in Israel, 16 of 56 (5 of 17 B, 10 of 32 C, and 1 of 7 A; p = 0.20 to 0.45) carried resistant virus, a significantly higher proportion (p=0.016) compared to that among patients infected in other countries, 7 of 114 (1 of 12 B, 6 of 68 C, 0 of 34 A).

Conclusions:  The frequency of resistant virus transmission within a group reflects the proportion of HIV carriers given antiretroviral treatment, the proportion of treated patients engaged in risky behavior, and factors such as adherence to treatment. We did not find significant differences in resistant virus transmission between the B and C groups, but a conclusive analysis should await a more extensive study. Drug-resistant virus was found in 24 of 170 (14.1%) recently infected patients. Of those who did not carry resistance-conferring mutations, at least 55% were infected in countries where drug treatment was not available (Ethiopia and former USSR). Of the 56 patients known to have been infected in Israel, 28.6% (16) had resistant virus, as compared with 11.1% found recently in Europe (the CATCH study). To what extent the difference is due to a more-complete treatment coverage in Israel and/or to a higher rate of risky behavior remains to be determined.

Keywords: Resistance in Naive Patients; Subtype C; Israel