[The need for the use of chromogens for quantifying Leishmania promastigotes on plates from 96 wells]

The existing difficulties in the treatment of leishmaniasis justify the testing of the effect of new products on parasite forms in the search of a therapeutic alternative for the parasitosis. Given the need of establishing a method to evaluate the activity of natural synthetic products in vitro under the Cuban conditions, this paper was aimed at defining the usefulness of p-nitrophenilphosphate as a chromogenic substance for quantification of parasites in plaques from 96 wells. To standardize this colorimetric method the stages of the parasite growth curve were set. The study of linearity and selection of the sample size, which was optional for these assays, showed that it was possible to obtain maximum linear determination coefficient with 20 mm. Likewise, the variation coefficient was compared with and without the chromogen and the effect of changes in culture medium on the reading of absorbances was analyzed. The set limit of quantification proved the need of using chromogen for the purposes of this paper and the general results allow to recommend this less subjective, simpler and quicker methodology to test products of interest in this field.