 This study found that 4 out of 40M tuberculosis strains had mutations associated with pre-XDRTB. These strains belong to lineage 4, which is the most common lineage in Zambia. Additionally, these strains were less cluster than other lineages, suggesting that they may be more transmissible. The study also found that three of the four strains belong to sublineage 4.3.4.2.1, which suggests that this particular sublineage may be responsible for the emergence of pre-XDRTB in Zambia. Furthermore, the study recommends strengthening routine drug susceptibility testing for second-line TB drugs to prevent further progression of pre-XDRTB to XDRTB and improve patient treatment outcomes. This article was authored by Joseph Yemuekichizomu, Edisamin Edisolo, Preciouswalia, and others.