Several protozoa (well there are lots of them, some very specific disease and symptoms, others more diffuse) seems hard to diagnose and hard to treat. Many of them seem quite resistant to protozoa drugs according to research.

I am wondering if there has been some testing on multi-drug therapy...

Think for Helicobacter (bacteria) it was first when they started with triple and even quadruple therapy that they got effective treatment method.

May be this is what is needed for many parasites that are hard to get rid off also.

Has anyone seen any research on this? For example many of the protozoa drugs seems to have some effect on many protozoa, but they are often alone not effective enough to give cure... what about combination therapies.