[Extensively drug resistant and extremely drug resistant tuberculosis forms after multi-drug resistant tuberculosis: new faces of the old disease].

Drug resistance in tuberculosis is a growing global problem. The emergence of multi-drug resistant tuberculosis cases, particularly in the 1990s, has become an important health problem and threatens tuberculosis control worldwide. Resistance to isoniazid and rifampicin, two of the most potent anti-tuberculosis drugs currently available, in multi-drug resistant tuberculosis cases is clinically quite important. The treatment of multi-drug resistant tuberculosis requires prolonged use of costly second-line drugs with significant toxic potentials under supervision and long-term hospitalization of patients. The appropriate management of tuberculosis, clinical/radiological and bacteriological follow-up, and surgery when needed are essential factors in the successful treatment of multi-drug resistant tuberculosis patients. An extensively drug resistant tuberculosis outbreak seen in KwaZulu-Natal region of the Republic of South Africa in 2005 led to certain doubts worldwide; this outbreak, introduced the importance and emergence of the counter measures against multi-drug resistant tuberculosis cases. Extensively drug resistant tuberculosis is defined as resistance to at least isoniazid and rifampicin from the first-line anti-tuberculosis drugs (the definition of multi-drug resistant tuberculosis) in addition to resistance to any fluoroquinolone, and to at least one of the three injectable second-line anti-tuberculosis drugs (kanamycin, capreomycin and amikacin) used in tuberculosis treatment. Mistreatment of multi-drug resistant tuberculosis cases by physicians, the use of anti-tuberculosis drugs with low quality, poor experience in management, lack of laboratories to perform second-line anti-tuberculosis drug susceptibility testing and problems in adherence of patients to treatment are factors associated to the development of extensively drug resistant tuberculosis. With the emergence of extensively drug resistant tuberculosis, World Health Organization gives importance to the mycobacteriology laboratory improvement, better multi-drug resistant tuberculosis case management, adequate drug supply, prevention of tuberculosis transmission and development of new drugs and diagnostics. Recently, a new form of tuberculosis, resistant to all first-and second-line anti-tuberculosis drugs seen in just a few number of cases, has been defined as extremely drug resistant tuberculosis and this is the end point in resistance problem in tuberculosis. In the view of this situation the stages of tuberculosis in terms of developing resistance are as follows: drugsensitive tuberculosis, mono-drug resistant tuberculosis, poly-drug resistant tuberculosis, multi-drug resistant tuberculosis, extensively drug resistant tuberculosis, and extensively drug resistant tuberculosis. In this review, the recent information about drug resistant tuberculosis forms, particularly extremely drug resistant tuberculosis that has been popular since 2005, has been discussed.