A patient with a cavitary lung lesion coughs up sputum that contains thin, acid-fast rods. Which of the following features would most likely be associated with these bacteria?

This is a history of pulmonary tuberculosis. Cell wall of M. tuberculosis is composed of waxy mycolic acids. Though all mycobacteria have gram-positive cell wall, gram staining is not done for staining of this group of organisms as the cell is covered with waxy mycolic acids. Therefore acid fast staining is done for these group of organisms