Infectiousness of drug-resistant Mycobacterium tuberculosis strains

October 2007, Vol. 97, No. 10 SAMJ Drug-resistant tuberculosis (TB), and especially multidrugresistant (MDR) TB (i.e. resistance to isoniazid and rifampicin with or without resistance to other drugs) or extensively drug-resistant (XDR) TB (i.e. MDR resistance plus resistance to the fluoroquinolones and one of the second-line injectables – kanamycin, amikacin or capreomycin),1 has very important implications for affected children and the TB control programme. These children are difficult to manage because of the increased adverse effects of the second-line anti-TB drugs and the prolonged duration of treatment. Furthermore, they are often diagnosed late because the history of a drug-resistant contact was not obtained or responded to. Children mainly have paucibacillary disease, which means that diagnosis of a child, especially with MDR TB, usually points to recent transmission in the community and therefore a failure of the TB control programme.