[Current microbiological methods in the investigation of mycobacteria]

The rapid and reliable detection of tuberculosis is the main goal of microbiological analyses. This is not only of great value for an early diagnosis and early start of an adequate therapy, but also helps to stop transmission and spread of the disease. Prerequisites for successful detection of mycobacteria are careful selection of patient specimens, proper sampling and appropriate shipping. In addition to the classical microbiological methods such as staining for acid-fast bacteria and culture procedures, newer molecular methods are gaining greater importance (PCR; NAT). TB bacteria and resistance-associated mutations can be detected from the specimens directly, providing an early hint about resistant strains. In positive cultures, M. tuberculosis complex and nontuberculous mycobacteria must be discriminated from each other. Drug susceptibility testing (DST) of all first-line drugs has to be performed from one isolate of each patient and repeated if TB bacteria are still isolated after 2 months of therapy. DST of second-line drugs should follow in case of drug resistance or drug intolerance.