CONCERN is mounting over a new strain of extra-deadly TB that arose in South Africa and could already be spreading elsewhere. But before you panic, help may be at hand: an international research collaboration has just signed a deal with China to develop a promising new class of TB drugs that should attack the strain, while two more types could be in final tests by later this year.
Extensively drug-resistant TB (XDR-TB) was first recognised last March. While strains of TB that resist the two most commonly used drugs have been emerging for years, XDR resists even the back-up drugs, making it almost untreatable. The World Health Organization has now confirmed it in 27 countries.
Last year scientists reported an outbreak of unusually aggressive XDR in KwaZulu-Natal Province in South Africa. It killed 52 of 53 infected at one hospital in under a month 鈥� an unprecedented death rate and speed for TB (New 杏吧原创, 16 September 2006, p 5). XDR has since been confirmed elsewhere in South Africa, though it is not yet clear whether this was the same super-aggressive strain.
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鈥淚t killed 52 of 53 infected at one hospital in under a month 鈥� an unprecedented speed and death rate for TB鈥�
There could be much more XDR out there. Maria Freire of the TB Alliance, a non-profit group that organises drug development, says very few TB cases in poor countries are tested for resistance, and many XDR infections may be 鈥渓atent鈥�, with no symptoms.
Moreover, an estimated half of XDR patients did not breed the resistance by skipping pills but caught bacteria resistant to start with. That and the KwaZulu-Natal cases suggest XDR can spread readily, meaning it could wreak havoc in the heavily HIV-infected populations in and around South Africa. The WHO is now launching urgent searches for it in such countries, while the European Union has urged affected nations to consider XDR 鈥渙ne of their highest-priority health problems鈥�.
If it is found, forcible quarantine of patients 鈥渕ay be necessary to protect the public鈥�, the WHO said in January. Patients with drug resistance and a history of failing to take TB medication have been forcibly quarantined in the past month in the US, Canada and Spain, in attempts to stop drug-resistant bacteria spreading.
What is needed, says Freire, is new classes of drug with novel ways of tackling TB. On 31 January, the TB Alliance announced funds for the Institute of Materia Medica in Beijing to seek drugs in a class called riminophenazines. These were considered promising in the 1950s but were abandoned for TB when early candidates caused skin discoloration, though one, clofazimine, is widely used against leprosy, a relative of TB.
Meanwhile, the alliance has two more new drugs heading for large-scale human tests. One, moxafloxacin, will be tested as a replacement for one or another of the major drugs in existing treatment regimens. So will another called PA824, which has a different mode of action.
