Microbiological diagnosis of infections caused by the genus Mycobacterium.

Mycobacterial culture has a high sensitivity and is the test of choice for the microbiological diagnosis of tuberculosis and nontuberculous mycobacterial infections. However, the results of this culture require at least 2-3 weeks to obtain positivity. Staining is rapid and can be used as a complementary study, although its sensitivity is low. Gene amplification tests have an intermediate sensitivity and obtain results in 1-2 days. These last tests are indicated in cases with moderate or high clinical suspicion. In HIV patients with severe immunodeficiency (<200 CD4), lipoarabinomannan antigen detection in urine may be useful. The identification of isolates from positive cultures is essential to evaluate the clinical significance of the culture results and consider the therapeutic options available. At present, there is a wide range of identification techniques available, which provide results within just 1-4 days. The future of diagnostic techniques in tuberculosis and nontuberculous mycobacterial infections lies in greater development of gene amplification techniques and promoting the search for biomarkers which enable a new approach to the diagnosis of these infections.