Comparative growth kinetics and drug susceptibility of Mycobacterium 2 tuberculosis lineages prevalent in Ethiopia: Implications for tuberculosis 3 treatment and management

Mtb strains, including sub-lineages 4.1.2.1, 4.2.2.2, 4.6.3, lineages 3 and 7, and the reference strain H37Rv (ATCC 27294), were cultured in liquid 7H9 Middlebrook broth. Growth began on day 6 post-inoculation. Sub-lineage 4.1.2.1 showed rapid exponential growth by day 9, reaching the stationary phase by day 15. Sub-lineage 4.1.2.1 followed by sub-lineage 4.2.2.2 had the highest maximum growth concentration (Cmax), indicating enhanced growth efficiency and adaptive traits that may increase their pathogenicity or resistance to host defenses or anti-TB drugs.