Microbiological diagnosis of tuberculosis

The increased incidence of tuberculosis as well as the availability of new diagnostic testing methods clearly have various implications for the routine microbiology laboratory: samples must be sent to the microbiology lab for testing immediately after being taken and microscopically investigated the same day. In other countries, difficult to treat, multi-resistant Mycobacterium tuberculosis strains have occurred. Thus decisive hygienic measures must be taken early on in cases of highly infectious patients (i.e. patients with microscopically positive sputum). Liquid media (MB Check Roche, Bactec) as well as L?wenstein Jensen media must be inoculated in the lab. Liquid media allow both faster detection of certain atypical mycobacteria and increased accuracy. Classification of culturally established agents through commercial genetic probes (AccuProbe Mycobacterien) or with high pressure liquid chromatography is possible within hours when acid-fast rods are present. Time consuming identification by determination of biochemical and culture morphological characteristics should be reserved for reference labs. Today, rapid tests like analysis of tuberculostearic acid or polymerase chain reaction are already useful for special questions like ruling out tuberculous meningitis. In most cases, however, these rapid tests cannot replace identification of microbes with culture techniques.