The role of the microbiology laboratory in diagnosing mycobacterial diseases.

Recent surveys show that many mycobacteriology laboratories continue to use less-than-optimal culture and susceptibility methods. This review summarizes available methods to diagnose. Mycobacterium tuberculosis. Although the local epidemiologic characteristics of M tuberculosis will partially determine what diagnostic measures are used, all laboratories should use a broth culture method in addition to a solid medium when culturing for M tuberculosis. Laboratories serving communities where drug resistance is common should use the BACTEC system for susceptibility testing or send isolates to a laboratory that uses it. Conventional testing in this setting must be aggressively discouraged. Rapid genetic amplification methods to detect mycobacteria in clinical specimens can greatly reduce the time needed to diagnose tuberculosis, especially if these methods can reliably detect M tuberculosis in smear-negative specimens. Many other diagnostic methods are being developed and clinicians and laboratories must regularly reassess whether a new method would be beneficial to their patients and the public.