Examining the ex vivo growth in the macrophages of Mycobacterium tuberculosis of various genotypic clusters

: To study the specific features of replication of Mycobacterium tuberculosis (MBT) strains of the W cluster in the macrophages (MP) on the ex vivo model of peritoneal MP of MBT-infected C57B1/6 mice, the authors estimated the viability of 6 antituberculous drug-sensitive MBT strains of the W-cluster from the incorporation of 5,6-[3H]-uracil into the mycobacterial cells and their induced specific MP from the level of LDH. Eight sensitive MBT strains of other genotypes clustered by the restriction fragment length polymorphism (PDRF) IS6110 and 2 laboratory strains M. tuberculosis H37Rv and M. tuberculosis H37Ra were taken as a control. The study indicated that, cultured in vitro, MBT strains belonging to different genotypic clusters differed in the level of 5,6-[3H]-uracil inclusion. When grown in MP, the MBT population of all genotypes showed a diminished viability as compared with that cultured without MP. The MBT clusters of W and AI clusters, unclustered strains, and M. tuberculosis H37Rv displayed a higher inclusion of 5,6-[3H]-uracil and the strains of KQ and HD clusters and M. tuberculosis H37Ra exhibited a significantly lower inclusion of 5,6-[3H]-uracil. W-cluster strains, the unclustered strain R807, and M. tuberculosis H37Rv showed the highest fitness (adaptability when grown in MP). The virulent strain M. tuberculosis H37Rv and avirulent strain M. tuberculosis H37Ra differed in MP viability by almost 5 times. Evaluation of the cytopathogenic effect indicated that the clinical MBT strains led to a specific MP lysis greater than 40%, the highest effect was produced by the MBT strains of the W cluster (more than 93%) and the HD cluster (96.45%). The control laboratory strains M. tuberculosis H37Rv and M. tuberculosis H37Ra contrasted sharply in their induced specific MP lysis (93.35 and 5.93%, respectively).