Application of ATP measurement to evaluation of the growth of parasitic protozoa in vitro with a special reference to Pneumocystis carinii.

1. There was a significant correlation between the increase in the number of Entamoeba histolytica, Trichomonas vaginalis, Giardia lamblia and Leishmania donovani in culture, and their ATP contents determined by luciferase reaction. 2. The similar correlation was also demonstrated between the decreased number of E. histolytica in the presence of an anti-amebic quassinoid and the nucleotide content in vitro. 3. In the case of Pneumocystis carinii, the numbers of the organism remained relatively constant in culture for at least 7 days without growth; however, the ATP content dropped rapidly in 1 to 3 days except in RPMI 1640. 4. The possibility that ATP determination of P. carinii is complicated by the host cell nucleotide seemed to be excluded, since the concentration of this nucleotide in normal lung was almost negligible. These observations suggest that the present procedure is useful for evaluating the growth and viability of these organisms in vitro.