[The intracellular multiplication of "Brucella" The theory for an experimental model (author's transl)]

Brucella melitensis can penetrate and multiply in cells of the BHK21 line. The intracellular bacteria can be counted either by culture after destruction of the cells or by direct examination after staining; in the latter case, the cells are distributed into various classes according to the number of bacteria which they contain. The number of intracellular bacteria increased exponentially and the division time is 12 hours. The intracellular division of the bacteria is independent of the cellular invasion. The infection by bacteria is not a factor related to mortality nor to survival of the cells. Whatever the number of bacteria initially placed on the BHK21 cells (up to 1,000 bacteria per cell), the number of infected cells never increased about 20%, and this indicates that all the cells do not have the same aptitude for the phagocytosis of Brucella. A mathematical model is suggested. Taking all factors into account, the model shows the probability for a certain number of Brucella per cell and, on the other hand, it shows the mean number of Brucella per cell at any particular moment. This model can be used in the case of other bacteria and of other cells, and can be used whenever a precise study of the intracellular multiplication of bacteria is required.