That the medicine chest is bereft of effective new drugs to fight the extremely drug-resistant tuberculosis (XDR-TB) strain has once again become frighteningly clear. According to a study published recently in The Lancet, while only 16 per cent (17 of the 107) of a South African patient cohort had either treatment cure or completion at the end of two years of follow-up, as many as 49 patients died and 25 failed treatment. With the strain remaining resistant to at least four of the most potent anti-TB drugs available today, XDR-TB patients have virtually exhausted all treatment options. Hence, despite long, complicated and prohibitively expensive treatment using toxic drugs, the outcome is at best poor. The dire urgency to bring immediate focus on the discovery of efficacious anti-TB drugs to treat all forms of drug-resistant strains becomes clear as hospitals in South Africa, for want of beds, are being forced to discharge XDR-TB patients who are yet to be cured. This is particularly ominous as they can spread the disease with equal ease as those with drug-sensitive TB. With the median survival period from the time of discharge being nearly 20 months, the threat of the dangerous form of TB spiralling out of control is real as many patients are culture-positive and about a third are smear-positive at the time of discharge; smear-positive patients have a higher bacterial load and hence a greater potential for spreading the disease. If this situation is allowed to continue for a few more years, the XDR-TB strain would spread to all countries.
There is also an immediate and pressing need for the high-burden countries to increase the number of beds for treating drug-resistant cases. It is time to come up with acceptable and workable solutions to isolate XDR-TB treatment failure or incurable cases to cut the transmission chain. Reducing the reservoir of TB-infected people through a simple, cheap and effective isoniazid preventive therapy in children under five years of age exposed to adults with pulmonary TB, will pay significant dividends in the long run. Next in priority should be ensuring that most drug-sensitive patients are diagnosed early, treatment using the correct drug regimen is initiated without delay, and the default rate is greatly reduced. This would automatically prevent the emergence of drug-resistant forms. The importance of this becomes all the more clear as all the parameters that go into the successful completion of drug-resistant TB treatment are fraught with problems. India, which is now expanding and equipping MDR-TB diagnostic centres with GeneXpert, has already detected 64,000 cases, the highest in the world.