Use of Living Chick Embryos in the Propagation of B. leprae

Because of our failure to obtain in vitro multiplication of B. leprae in minced chick embryo media, 1 it occurred to us that living chick embryos might afford a more suitable nutritive since the studies of Duval 2 indicate that B. leprae is unable to cleave whole protein and that the split products (amino acids) are essential for its multiplication. This hypothesis is substantiated by the observations that the bacilli apparently enter and colonize within the living host cells without destroying them and, as intracellular sojourners, utilize the nutrients intended for the latter; that artificial culture media containing the end products of protein digestion afford a favorable foodstuff for the initial cultivation of B. leprae; and that in removed bits of leprous tissue in which autolysis has taken place, the Hansen rods continue to proliferate so long as there are amino-acids present, while in subsequent transplants from these bits of tissue, growth becomes more feeble as the protein split products decrease in amount. Further, the living chick embryo was thought a desirable medium since it is known that there is a large supply of split protein accessible to its growing cells. The question of susceptibility of the living chick embryo to leprosy and the adaptation of B. leprae to this environment was considered. In this connection, it is realized that very few lower animals are susceptible to B. leprae propagation.

The object of this study was to determine the time required for the growth and multiplication of B. leprae in the living chick embryonic tissue, the modus operandi of the invasion and the effects of colonization upon the living cells. That part of the study which deals with the time required for in vivo cultivation of B. leprae will be considered in this paper.