a method of inducing latency in mycobacterium permits preparation of an in vitro model system of latent mycobacterial infection . latency is induced in a pure culture of mycobacterium by exposing it to multiple stress conditions , including a low nutrient culture medium without glycerol , a low ph , a relatively high level of carbon dioxide and a relatively low gas phase oxygen level . an in vitro model of mycobacterial infection employs macrophages induced from thp1 cells which are then infected with mycobacterium . the infected macrophages are grown under hypoxic conditions to induce latency in the mycobacteria . the in vitro model of infection is useful in evaluating compounds for activity against latent mycobacteria .