How is etiology of TB?

Complex of bacteria (M.tb, M.africanum, M.bovis, M.microti. Other mycobacteria are non-TB organisms. Non-spore forming, non-motile, obligate aerobe, catalase -, intracellular bacteria that is acid-fast. Weakly gram+ cells may appear on gram stain (Called Ghost cells) Presence of several lipids in cell wall (mycolic acid, cord factor, Wax-D) is unique for it, which contributes to its infection properties (resistance to Abx, difficult gram stain, survival in extreme conditions. Ziehl-Neelsen stain is used to dx TB (carbol fushion stain) decolorize with acid-alcohol, counter stain (+ pink color for TB)