The growth kinetics of intracellular bacille calmette-guerin (BCG) within human monocyte-derived macrophages of different ethnic populations.

Abstract

In this paper we have examined intracellular mycobacterial growth in human monocyte-derived macrophage cell cultures. Cells from three population groups were selected to compare and contrast the kinetics of intracellular BCG growth both by determining changes in metabolic activity of dividing bacteria by radioisotope incorporation and growth/survival by estimating colony forming unit by Fatal's Microcolony Counting Method. These data indicate that BCG infects and multiplies intracellularly in human macrophages and may serve as an in vitro model for studying inherent capability of mycobacteria to grow and infect macrophage populations. There is however, no inhibition or reduction of intracellular mycobacterial growth from a Caucasian male and female, and an Afrocarribean female donor macrophages. On the contrary, there is a ten-fold increase in the replication of mycobacteria over a 7-day infection period. Patterns of BCG growth within macrophage cultures from different donors were determined and variation calculated at different days post-infection. Experiment to experiment coefficient of variation of intracellular 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%.