Every year approximately 1.5 million people worldwide die of tuberculosis (TB). The pathogen’s resistances to antituberculotics play a major role, as they make it more and more difficult to control TB. Resistant tuberculosis is often more difficult to treat and patients remain infectious for a longer time. There are primary resistances that already exist before therapy is started and secondary or acquired resistances that arise after initiation of an antituberculotic therapy. Frequent causes of resistance development are monotherapy, discontinuous intake of medication, wrong dosage, poor quality of drugs or malresorption. In order to avoid resistance development, TB is always treated with a combination of different drugs for a period of at least six months.
Monoresistance describes a resistance to a first-line drug like isoniazid, rifampicin, pyrazinamide, ethambutol or streptomycin. First-line drugs are used in the standard therapy of TB.
Multidrug-resistant tuberculosis (MDR-TB)
The World Health Organization (WHO) defines MDR-TB as a form of TB where the pathogen is resistant to at least isoniazid and rifampicin, the two most effective first-line drugs.
Extensively drug-resistant tuberculosis (XDR-TB)
According to the Centers of Disease Control and Prevention (CDC), XDR-TB is defined as TB caused by bacteria that are resistant to rifampicin and isoniazid as well as to any one of the fluoroquinolones and to one of the injectable second-line drugs (amikacin, capreomycin or kanamycin). XDR-TB emerges through mismanagement of treatment of MDR-TB patients. XDR-TB can be found all around the world. Due to the limited treatment possibilities, successful XDR-TB treatment is rare.
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