[Treatment of tuberculosis according to the different pattern of resistance]

When the complexity, efficacy, costs and side effects of tuberculosis (TB) treatment are analyzed, we can observe important differences according to the drug resistance pattern. In order to simplify this complex management, there are six serial levels of complexity: a) susceptible to all drugs, b) resistance to isoniazide or rifampicine but not to both, c) TB multiresistance (at least to isoniazide and rifampicine, d) TB multiresistance plus resistance to fluoroquinolones or to injected agents, but no to both groups of drugs, e) TB multiresistance plus resistance to fluoroquinolones and injected agents, which would be the two most effective, second line groups of drugs. Neither the group 4 nor group 5 correspond exactly to the currently accepted definition of extensively TB multiresistance (TB-XDR: TB multiresistance plus resistance to fluoroquinolones and, at least, to one of the second-line injected agents), which perhaps is not the most adequate definition, as we will discuss. f) Finally, there is the recently defined totally resistant TB (TB-TDR), which implies resistance to all first-line drugs and to the six second-line groups (fluoroquinolones, aminoglycosides, polypeptides, thiamines, cycloserine and para-amino-salycilic acid [PAS]). The management becomes more complex in all aspects and the prognosis worsens clearly as the level of resistance increases. We analyze here these different and progressive resistance levels from both the therapeutic and prognostic perspectives.