Identification of mycobacteria is performed at reference centres, and is based on morphology, growth and biochemical characteristics. M. tuberculosis needs to be distinguished from other mycobacteria, for which treatment may be different and there are no infection-control concerns. Cultures are central to the confirmation and identification of the mycobacterium, and for drug susceptibility testing. More rapid results are obtained from liquid media, which usually grow M. tuberculosis in 7–28 days. Drug susceptibility tests are usually available within 10–21 days of the laboratory receipt of isolates and are performed using standard assays.