THE GROWTH-KINETICS OF INTRACELLULAR BACILLUS-CALMETTE-GUERIN (BCG) WITHIN HUMAN MONOCYTE-DERIVED MACROPHAGES OF DIFFERENT ETHNIC POPULATIONS

In this paper we have examined intracellular mycobacterial growth in h uman monocyte-derived macrophage cell cultures. Cells from three popul ation groups were selected to compare and contrast the kinetics of int racellular BCG growth both by determining changes in metabolic activit y of dividing bacteria by radioisotope incorporation and growth/surviv al by estimating colony forming unit by Fatal's Microcolony Counting M ethod. These data indicate that BCG infects and multiplies intracellul arly in human macrophages and may serve as an in vitro model for study ing inherent capability of mycobacteria to grow and infect macrophage populations. There is however, no inhibition or reduction of intracell ular mycobacterial growth from a Caucasian male and female, and an Afr ocarribean female donor macrophages. On the contrary, there is a ten-f old increase in the replication of mycobacteria over a 7-day infection period. Patterns of BCG growth within macrophage cultures from differ ent donors were determined and variation calculated at different days post-infection. Experiment to experiment coefficient of variation of i ntracellular BCG growth estimates for a single donor is between 4-12%. In contrast, the coefficient of variation of intracellular BCG growth between three different macrophage donors studied is < 4%.