The infection and the post-infection incubation were performed in the absence or presence of 0.25 μg/ml Tetracycline: (-/-), Tet was never added to the medium; (+/-), trypomastigotes were pre-treated with Tet for 3 hours prior to infection, and it was added during the infection but not after; (-/+), trypomastigotes were not induced, Tet was only added for 48 hours post-infection at the amastigote stage; (+/+), trypomastigotes were pre-treated and Tet was present at all times. The conditions (-/-) and (+/+) were also tested in the presence of 75 μM Nicotinamide (+ NAM). The percentage of infected cells (A) and the number of amastigotes per cell (B) were determined by counting Giemsa-stained slides using a light microscope. Results are expressed as means ± SEM of triplicates, and represent one of three independent experiments performed. Each condition was analyzed by unpaired Mann-Whitney two-tailed Student t test with the control (-/-): * p<0.05, ** p<0.005, *** p<0.001. The same statistical analysis was used to compare uninduced and induced parasites in the presence of NAM (-/-, +NAM and +/+, +NAM): σ p<0.05.