Flow cytometry analysis of drug transport mechanisms in Haemonchus contortus susceptible or resistant to anthelmintics.

The role of membrane drug-transport mechanisms in resistance to anthelmintics was examined using a flow cytometry method. This method was adapted from assays developed for the study of similar mechanisms in tumor cells. Rhodamine 123, a P-glycoprotein transport probe, associated with the reversal agent verapamil gave a significantly higher level of green fluorescence in Haemonchus contortus-resistant eggs as compared with that of susceptible eggs. In the same way, verapamilbodipy, a new fluorescent probe for the detection of multidrug resistance in cells, showed a significantly higher degree of binding to resistant eggs. The results confirm those obtained with biological drug assays using both anthelmintics and verapamil and provide a quantitative and effective methodology for the functional study of multidrug resistance in nematodes.