According to an article in POZ, an individual contracted a multi-drug resistant strain of HIV while keeping to a daily dosage of Truvada (tenofovir/emtricitabine), commonly known as PrEP (pre-exposure prophylaxis). Researchers determined that it is indeed possible for individuals who follow a PrEP protocol can contract HIV when exposed to a virus that resists the drugs included in Truvada.
Home Lifestyle Health and Fitness First Documented Case of HIV Transmission to Patient Using PrEP (Truvada)