Extensively drug resistant tuberculosis

Tuberculosis outbreaks in the developed world are newsworthy. However in the developing world where deaths from tuberculosis are common it takes something exceptional for an outbreak to attract much attention. In response to a recent report at the 16th international AIDS conference and to increasing South African media reports the World Health Organization last week expressed concern about extensively drug resistant tuberculosis (also referred to as XDR tuberculosis). Among 536 culture confirmed cases of tuberculosis at a rural hospital in South Africa 41% were multidrug resistant defined as resistance to rifampicin and isoniazid (two key first line drugs). This is cause enough for concern as multidrug resistant tuberculosis has a worse outcome and its management is very difficult even in high resource settings. Even more alarming was that 53 (24%) of the isolates from multidrug resistant tuberculosis fulfilled the definition of extensively drug resistant tuberculosis--namely multidrug resistant tuberculosis that is also resistant to at least three of the six classes of second line agents. Such tuberculosis is virtually untreatable. (excerpt)