(A) Doubling time at the exponential growth phase of in vitro cultures of different passage numbers: P1, P5, P11, P21 and P41 (abcd groups with no common superscript letter differ significantly; P<0.05). (B) Bioluminescence and fluorescence values of 1x105 parasites taken from 2-days old in vitro cultures of different passage numbers: P1, P5, P11, P21 and P41. Columns represent the median values and the interquartile range (ABCabc groups with no common superscript capital letter differ significantly for bioluminescence, and groups with no common superscript small letter differ significantly for fluorescence; P<0.05). (C) Representative photomicrograph of P41 ‘Ld1S_luci_E2-crimson’ promastigotes to illustrate the constant expression of the red fluorescent protein.