Question: Have you ever found a parasite or infection that was resistant to any test you've done on it?

Tim Downing answered on 12 Nov 2012:

Unfortunately, yes. The parasite I study evolves drug resistance really quickly – eg within just a decade. This may seem long but we need drugs to be effective for a long time because they take so long to develop. For example, ten years ago, heavy-metal (antimonial) drugs were the first defence against Leishmania (“leash-mane-ee-aa”) in India/Nepal but now they only work in certain patients. So doctors brought out a new fat-based drug called miltefosine that attacks cell membranes by distrubing the isotonic balances of anions and cations (sometimes called minerals in our food). This causes the cells to explode. But even now the new drug doesn’t work very well.

We can even make drug-resistance parasites in the lab by growing them with progressively higher doses of the drugs so that they adapt but don’t die. This lets us predict how quickly resistance might emerge. So for certain drugs this is long or short, and by knowing this we hope to be able to determine which drugs are best to take.

Tim