Antibiotic-Resistant Tuberculosis: Glimpse of Hope for Most Deadly Infectious Disease in the World

File photo: A campaign raises awareness of tuberculosis. Getty Images

Tuberculosis (TB) is the most deadly infectious disease on the planet, affecting a quarter of the world's population and killing more than 1.5 million people every year. Although overall TB rates are falling, rising antibiotic resistance threatens recent strides made against this devastating disease.

But a genomic analysis of the most common form of TB offers a glimpse of hope. Drug-resistant strains tend not to spread internationally, a study published in the journal Science Advances has shown. This means countries that successfully tackle transmission could see their drug-resistant TB rates plummet.

"In a worst-case scenario, the emergence of antibiotic-resistant strains could reverse the gains that have been made in recent years," study author Vegard Eldholm, from the Norwegian Institute of Public Health, told Newsweek. "[Certain] resistant infections are notoriously hard to treat and too often result in the death of patients."

Eldholm and the team probed 1,669 TB samples from around the globe—ancient and modern—to build a better picture of the rise of Lineage 4 and the spread of resistant strains. "We applied a number of sophisticated analysis tools combining temporal, spatial and genomic data," study author Francois Balloux, from University College London, told Newsweek. "This allowed us to generate robust estimates of how Lineage 4 TB has evolved and spread globally, including where and when antibiotic resistance has emerged."

Although TB emerged in Africa 4,000-6,000 years ago, the results suggest European colonialists spread what is now the most common type of TB—Lineage 4—to Asia, Africa and the Americas. Lineage 4 appeared in Europe about 1,000 years ago, and its spread into individual countries, including the Republic of Congo, Uganda and South Africa, closely matches the timing of European colonial expansion.

Drug-resistant strains of Lineage 4 TB developed more recently, but generally stay contained within individual countries, the research shows. "There is no doubt that resistant strains can spread between countries," Eldholm said. "But what we see very clearly is that—at least up until now—[local epidemics and outbreaks of drug-resistant] Lineage 4 TB have had very limited impact on neighboring regions."

The results won't directly alter the way healthcare professionals fight TB, Eldholm said, but they offer hope for halting the spread of drug resistance in the future. "The limited international spread of drug-resistant TB suggests that the scourge can be fought successfully at the level of individual countries, which represents excellent news and justifies local TB programs," Balloux said.

For the first time in decades, there are new anti-TB drugs on the market and new developments to aid diagnosis of resistant TB on the horizon, Eldholm added.

Like any scientific study, these latest results are limited. Lineage 4 may well be the most common form of TB, but it's not the only type facing resistance. "Alarming levels" of drug resistance can be found in Lineage 2, also known as the Beijing Lineage. "To get a more complete view of how resistant TB spreads globally, it will be critical to include [this]," Balloux said.

"For scientists, it will be essential to keep tracking resistant TB so that we pick up new trends in resistance and how resistant strains move as early as possible," Eldholm added. "This will enable the global TB and public health community to respond with targeted interventions and measures rapidly when a new situation emerges."