Researchers have identified a new strain of tuberculosis in 17 patients in the Eastern Cape which is totally resistant to the all current drug regimens.
When an earlier study of extensively drug resistant (XDR) TB in the Eastern Cape showed that patients weren't responding to treatment - 58 percent of patients died within a year and only 8.4 percent became un-infectious after more than four months of treatment – epidemiologists at Stellenbosch University (SU) decided to investigate the bacteria that seemed to be more resistant against the available drugs. The Eastern Cape cases are the first to be identified in South Africa, and the fourth country in the world to report totally drug resistant (TDR) TB – it was discovered in India last year, and in Italy (2003) and Iran (2009).
What they found was an emerging strain of TB even more resistant to drugs than XDR, which is already resistant to all first line drugs and some second line drugs. This new strain has shown resistance to at least 10 anti-TB drugs currently in use in the health sector.
According to Prof Tommy Victor, from SU's Division of Molecular Biology and Human Genetics, the World Health Organisation and many experts in the field, including him, think the name "totally drug-resistant" (TDR), which is currently used in scientific literature, is not appropriate. They believe there may be a cure for TDR among some of the new drugs currently being developed, or old medication not in use anymore.
"We really are facing bacteria that has become increasingly resistant, and there are now some bacteria that are hyper resistant, irrespective of the definition," said Victor who was one of the authors of the study.
In the scientific paper, which was published in the Emerging Infectious Disease Journal in March this year, they used molecular techniques to study cultures of the tuberculosis bacterium of just under 400 Multi-drug resistant (MDR) TB patients in the Eastern Cape. Among these a large number were pre-XDR and XDR's, and 17 cases of TDR.
There are approximately 18 000 new MDR cases diagnosed each year and "there may be be more TDR cases in South Africa ," says Victor, explaining that 17 cases emerged from only 400 MDR samples tested.
A shortcoming of the study, which was acknowledged by the authors, is that they only studied the cultures from the infected patients, and don't have any data on patient outcomes – so they don't know how long they may have survived, or if any have been cured. Although a related study on the Eastern Cape cohort showed that patients responded quite badly to even the fiercest treatment.