Abstract

This chapter covers the available techniques for the diagnosis of tuberculosis (TB) and drug resistant tuberculosis. Definite diagnosis of tuberculosis requires the isolation on culture or the identification by molecular biology methods of M. tuberculosis (Mtb). Resistance to antituberculosis drugs, once Mtb has been identified can be carried through conventional culture methods (phenotypic methods) or molecular biology (genotypic methods). Ideally, susceptibility to at least isoniazid and rifampin should be carried in every case, especially in regions with high burden of drug resistant TB. The World Health Organization (WHO) recommends that at least 20% of all new cases and 100% of previously treated patients should be tested for drug resistance. Although the isolation of Mtb in cultures is still considered as the gold standard, advances in the field of molecular biology allows for a much rapid identification of Mtb, with excellent sensitivity and specificity. Drug susceptibility testing by phenotypic methods can be carried out in both solid and liquid media, but this process is slow, especially with the time-honored proportions method; we now have available molecular biology methods with excellent reliability for isoniazid and rifampin with results in a matter of hours.