Figure 1. Stability of resistance to drugs in L. donovani promastigote lines.

(A) The stability of resistance with respect to the initial EC₅₀ (black columns) is determined at 1 (gray columns) and 4 months (white columns) after removal of the drug pressure. The results shown are the average of three independent experiments ± SD. Significant differences versus the initial EC₅₀ were determined using Student's t-test (*: p<0.05; **: p<0.01; ***: p<0.005; ****: p<0.001). (B) Results from panel A expressed in terms of the resistance index. The horizontal black line represents a resistance index of 1 equivalent to a completely loss of resistance. ^a: line that lose resistance after 1 month in a drug-free medium; ^b: line that maintain similar initial resistance levels after 4 months in a drug-free medium.