Bacteriology of Tuberculosis
Although a search for acid-fast bacilli (AFB) on stained sputum smear, and culture and drug-sensitivity testing on enriched agar or egg-based medium are still the basic methods for the laboratory diagnosis of tuberculosis, they are far from being accurately implemented or performed in a majority of countries in the world, and a complete set of new technologies is now available. The use of a radiometric detection system for mycobacterial growth permits a reduction of the time required for obtaining the results of culture and drug-sensitivity tests. Nonisotopic probes for the identification of pure cultures and DNA fingerprinting of Mycobacterium tuberculosis for strain typing are important new developments. In addition, the application of nucleic acid-amplification techniques to the direct detection of M. tuberculosis in clinical specimens and the direct detection of drug resistance, especially to rifampin, is offering new tools, although they are still relatively expensive and sophisticated. The purpose of this chapter is to present conventional and modern methods for the laboratory diagnosis of tuberculosis in a pragmatic approach for developed as well as for developing countries.