Dr. Andreas Diacon from Stellenbosch University in South Africa offered an update on MDR and XDR Tuberculosis from his vantage point as a clinician and researcher in South Africa. One percent of the South African population is diagnosed with active tuberculosis every year—a huge disease burden.
He noted that when they are able to treat the patient with active TB, they generally get it right and do not see too much acquired resistance. Acquired resistance is generally a by-product of poor drug quality or poor adherence. But in South Africa, more than 75 percent of MDR-TB is found in patients who have not previously been treated for tuberculosis. In these cases, individuals are infected with a drug resistant strain either in the community or in a health care setting. They expect 16,000 cases of MDR-TB in 2010 in South Africa, and the cost of treating drug-resistant tuberculosis is more than 50 percent of the country’s entire TB budget.
From his perspective, current WHO guidelines are more appropriate for low TB prevalence settings, because they don’t call for diagnosis of drug resistant tuberculosis until people actually fail TB therapy. He argued that in the South African high TB prevalence environment, they should be doing molecular drug susceptibility testing up front, but this is a cost issue.
XDR-TB is a treatable disease although mortality is very high. XDR is found in HIV negative individuals and it is very clear that it can be transmitted. The high burden of HIV infection has clearly compounded the challenge of getting the TB epidemic under control. HIV infected persons are more susceptible to TB infection and are more likely to develop the disease. When treated, there is slower culture conversion so they are infectious to others for a longer period of time.
He also noted the low uptake of TB prophylactic therapy—so called isoniazid preventive therapy or IPT—especially for HIV infected individuals. He attributed this to the huge concerns clinicians have about isoniazid resistance, especially in the context of high numbers of drug-resistant TB patients. He suggested that if another drug were available for prophylactic therapy other than isoniazid—one of the backbone drugs of the basic TB treatment regimen, there would be much greater uptake of this intervention.
While he acknowledged that the current TB drug pipeline was larger than it had been for decades, he called it completely inadequate to respond to this ancient disease, still responsible for nearly 2 million deaths a year.