Antituberculosis drugs multidrug resistance

Multidrug resistance The most recent cultures should undergo susceptibility testing to all antituberculosis drugs if cultures remain positive after 3 to 4 months of treatment. 

Treatment problems that can arise are mainly of two types adverse reactions (collateral, toxic, or hypersusceptibility reactions), and initial or acquired resistance of Mycobacterium tuberculosis, Mycobacterium bovis, or non-tuberculous mycobacteria to one or more of the antituberculosis drugs. The latter probably only occurs when the patient has not taken the full combination or the full doses of the drugs all the time. Combination formulations are thus particularly useful. Multidrug-resistant tuberculosis, defined as resistance against at least isoniazid and rifampicin, is the most clinically relevant form of resistance to treatment worldwide. 

Multidrug-resistant tuberculosis generally results from inadequate therapy or lack of compliance with therapy. A strain of mycobacteria is called resistant when it is insensitive to one of the first-line drugs. It is called multiresistant when it is insensitive to both isoniazid and rifampicin. In this case other antituberculosis drugs may also be ineffective (35). In practice, at least two second-line antituberculosis drugs, selected on the basis of individual drug susceptibility, are given in combination with a fluoroquinolone (36). 

In an in vitro susceptibility study of 170 clinical isolates of Mycobacterium tuberculosis to fusidic acid, 19 isolates were resistant to at least one first-Une antituberculosis drug (21). In all, 1.8% of the isolates were resistant to fusidic acid. Fusidic acid can be a potential supplementary drug for the treatment of infections due to multidrug-resistant strains of M. tuberculosis. 

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