FIG. 1.

Reduction of alamarBlue by different plating densities of A. castellanii (a) and A. polyphaga (b) cultures in 100 μl (closed squares) and 200 μl (closed circles) of medium over 6 h. In the 100-μl cultures, 95 and 88% alamarBlue reductions were achieved over this time period by 5.0 × 10⁴ A. castellani and A. polyphaga cells per well, respectively. In comparison, with the 200-μl cultures, maximum reductions of 53 and 60% alamarBlue were achieved by 5.0 × 10⁴ A. castellani and A. polyphaga cells per well, respectively. The results are expressed as the means for triplicate cultures ± SEs. (c to f) AlamarBlue reduction had a linear correlation with Acanthamoeba cell number, irrespective of the species or the culture volume, up to 5 × 10⁴ parasites per well (P < 0.05).