"These results show that XDR tuberculosis is increasingly a cause for concern, especially in areas where prevalence of MDR tuberculosis is high," Sven Hoffner of the department of preparedness at the Swedish Institute for Communicable Disease Control in Sweden writes in a commentary to accompany the new study.
"The true scale of the burden of MDR and XDR tuberculosis might be underestimated and seem to be rapidly increasing."
While experts grow increasingly concerned about the growing resistance of antibiotics to tuberculosis, some advocate a different approach -- prevention.
"The genome of tuberculosis is highly plastic, so we will always be 'chasing our tail' in terms of antibiotic-driven approaches," says Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine and president of the Sabin Vaccine Institute. "This study points to the urgency for accelerating the development of a [tuberculosis] vaccine."