Background:  In resource-limited settings where ART access is being rapidly expanded, WHO recommends surveillance of transmitted HIV drug resistance. The recommended method is the threshold survey, which uses as many as 47 consecutively collected specimens to classify HIV drug resistance prevalence as low (<5%), medium (5 to 15%), or high (>15%). The recommended target population is “recently infected” HIV⁺ persons represented by HIV⁺ primagravid women under age 25 years attending antenatal clinics (ANC). We conducted a survey to assess transmitted HIV drug resistance in Dar es Salaam, where ART was first introduced in 1995 and about 11,000 patients currently receive it.

Methods:  From November 2005 until February 2006, during the HIV ANC sentinel survey, dried blood spot (DBS) specimens were collected using remnant specimens from 47 eligible women who consecutively attended ANC for routine syphilis testing. Total HIV-1 nucleic acids were extracted from DBS at the Centers for Disease Control and Prevention, Atlanta, Georgia, using a modified NucliSens^® silica-based extraction method. The protease and RT region of HIV-1 genome was amplified with an in-house real-time polymerase chain reaction (RT-PCR) method and sequence analyses were performed with an ABI 3100 Genetic Analyzer. Protease and RT genotypes were generated using Stanford University HIV drug-resistance database.

Results:  Among 3563 DBS specimens collected, 68 were from women meeting the eligibility criteria. Of these, 49 DBS were RT-PCR-positive and 34 were sequenced. Phylogenetic analysis showed that there were 12 (35.3 %) subtype C, 10 (29.4%) sub-subtype A1, 4 (11.8 %) subtype D, 2 (5.9%) each of subtype C/A1, CRF08/C and D/CRF10, and 1 (2.9%) each of A1/D and CRF15/A1. Based on the WHO mutation list for surveillance of transmitted drug resistance, no resistance-associated mutations were seen. Polymorphic mutations not indicating transmitted resistance include RT mutations V75L, Y108I/L, Y115I, and V118I (1 of 34), and protease mutations M36I (30 of 34), L63A/I/K/P/Q/S/T/V (23 of 34), L10I (20 of 34), I93L (16 of 34), K20I/Q/R/T (6 of 34), M46L and A71T (2 of 34), and F53Y (1 of 34). None of these substantially affect HIV drug resistance, except M46L, which is associated with low-level resistance to some protease inhibitors.

Conclusions:  Our survey indicates that prevalence of transmitted HIV drug resistance among recently infected pregnant women in Dar es Salaam is low (<5%).