A centuries-old herbal medicine, discovered by Chinese scientists and used to effectively treat malaria, has been found to potentially aid in the treatment of tuberculosis and may slow the evolution of drug resistance.
In a promising study conducted at Michigan State University in the United States, the ancient remedy artemisinin was found to stop the ability of TB-causing bacteria, known as Mycobacterium tuberculosis, to become dormant. This stage of the disease often makes the use of antibiotics ineffective.
When TB bacteria are dormant, they become highly tolerant to antibiotics. Blocking dormancy makes the TB bacteria more sensitive to these drugs and could shorten treatment times, said the researchers.
One-third of the world's population is infected with TB and the disease killed 1.8 million people in 2015, according to the US-based Centers for Disease Control and Prevention (CDC).
Mycobacterium tuberculosis (Mtb) needs oxygen to thrive in the body. The immune system starves this bacterium of oxygen to control the infection. The research team found that artemisinin attacks an oxygen sensor in Mtb and by disrupting this sensor it stopped the disease's ability to sense how much oxygen it was getting.
The study showed that when the Mtb is starved of oxygen, it goes into a dormant state, which protects it from the stress of low-oxygen environments. If Mtb cannot sense low oxygen, then it cannot become dormant and will die.
Dormant TB can remain inactive for decades in the body. But if the immune system weakens at some point, it can wake back up and spread. Whether it wakes up or stays 'asleep' though, TB can take up to six months to treat and is one of the main reasons the disease is so difficult to control.
The research team pointed out that patients often do not stick to the treatment regimen because of the length of time it takes to cure the disease, and incomplete therapy plays an important role in the evolution and spread of multi-drug resistant TB strains.
The new research could be key to shortening the course of therapy because it can clear out the dormant, hard-to-kill bacteria. This could lead to improving patient outcomes and slowing the evolution of drug-resistant TB.
After screening 540,000 different compounds, the researchers also found five other possible chemical inhibitors that target the Mtb oxygen sensor in various ways and could be effective in treatment as well.
Two billion people worldwide are infected with Mtb and TB is a global problem that requires new tools to slow its spread and overcome drug resistance. This new method of targeting dormant bacteria is exciting because it shows us a new way to kill it.