Requirements of defined cultivation conditions for standard growth of Leishmania promastigotes in vitro.

The growth characteristics of L. chagasi (MHOM/BR/79/LI01) and L. braziliensis (MHOM/BR/72/1670), the causative agents of visceral and muco-cutaneous leishmaniases, respectively, were compared. Inoculum size clearly influences the growth course of both Leishmania species, whatever the culture medium used (serum-supplemented media: GLSH or RPMI, and a chemically defined medium: LITR9). Cultures initiated with low concentrations failed to promote cell growth, while typical growth curves were obtained when higher promastigote inocula were used. For all the species tested, the higher the initial density of flagellates in the medium, the shorter were the periods covered by the latent and particularly by the logarithmic growth phases. In contrast, using constant inocula, variations in the volume of the incubation medium did not change the time-course of the different culture phases of either Leishmania species, provided that the ratio of incubation medium to total flask volume was comparable. Only cell division time significantly increased with the culture volume. We also determined whether or not the growth characteristics of the promastigotes of L. chagasi or L. braziliensis could be generalized to other members of the genus. Our results show that, whatever the culture medium used, L. infantum behaves in the same way as does L. chagasi, whereas L. panamensis, L. guyanensis, L. mexicana and L. amazonensis display growth patterns similar to that of L. braziliensis.