Reply to Vargas and Farhat: <i>Mycobacterium tuberculosis glpK</i> mutants in human tuberculosis

We thank Vargas and Farhat (1) for their analyses confirming that reversible glpK frameshifts are common within human Mycobacterium tuberculosis infections. In their thoughtful comments they suggest that additional forces, other than antibiotic pressure, may contribute to the emergence of these mutants. We agree that the mechanisms by which glpK mutants are selected may be complex; however, we question whether their study can resolve if antibiotic pressure in human tuberculosis (TB) increases the fitness differential between wild-type and glpK frameshift M. tuberculosis . Vargas and Farhat (1) describe their experience sequencing the glpK gene in M. tuberculosis cultures isolated from the sputum samples of 200 longitudinally followed … [↵][1]2To whom correspondence may be addressed. Email: david.alland{at}rutgers.edu. [1]: #xref-corresp-1-1