The laboratory diagnosis of mycobacterial disease.

The diagnosis of mycobacterial disease still relies heavily on conventional microscopy and culture techniques. More modern methods, such as the Bactec 460 radiometric system and the Roche biphasic system, are becoming available but are not yet widely used. Non-culture methods eg, using molecular biology techniques or gas liquid chromatography, are being developed but are currently the province of research and reference laboratories. Disease caused by species other than Mycobacterium tuberculosis poses problems of diagnosis and treatment. These other species can be identified by comparatively simple techniques but, as they are widely distributed in the environment, deciding between casual contamination and true infection can be difficult. Although such infections are not a major problem in numerical terms, the variable response of patients to treatment means that conventional sensitivity testing is of little assistance, and it is necessary to seek evidence of synergy in drug combinations for the effective treatment of these infections.