Detection of arsenical drug resistance in Trypanosoma brucei with a simple fluorescence test.

The resurgence of human African trypanosomiasis (HAT), coupled with an increased incidence of drug resistance, is of concern. We report a quick, simple, and sensitive test for identification of parasites resistant to melarsoprol, the main drug used to treat late stage HAT. Resistant parasites are defective in a plasma membrane transporter responsible for drug uptake. The same transporter carries the fluorescent diamidine DB99 (2,5-bis-(4-amidinophenyl)-3,4-dimethylfuran) into trypanosomes. The two DNA-containing structures in the trypanosome--the nucleus and the kinetoplast--begin to fluoresce within 1 min of introduction of DB99, unless drug resistant.