Answer;
-Evolution
Explanation;
Drug-resistant TB remains a significant challenge in TB treatment and control programmes worldwide. Drug resistance in M. tuberculosis is caused by the acquisition of mutations in genes that code for drug targets or drug-activating enzymes. The evolution of strains resistant to multiple antibiotics is driven by the sequential acquisition and accumulation of resistance-conferring mutations on the bacterial chromosome.
Drug resistance occurs due to; primary or transmitted drug resistance, which occurs when resistant strains are transmitted to a new host, and the secondary or acquired drug resistance, which occurs through the acquisition of drug resistance mutations to one or more drugs.