Researchers from the Albert Einstein College of Medicine reported this week that a combination treatment made up of two FDA-approved drugs may be able to treat tuberculosis (TB) that is resistant to standard TB drugs. If true, the new treatment could help hundreds of thousands of people worldwide who suffer from multidrug resistant TB (MDR-TB), which does not respond to the two most common antibiotics used for TB, and extensively drug-resistant (XDR-TB) bacteria that resist at least four of the drugs used to treat TB.

In the study, published Thursday in the journal Science, the researchers used cultures of TB bacteria in a lab to show that the combination of the antibiotic meropenem and another drug called clavulanate is effective against 13 different strains of XDR-TB, the hardest type of TB to treat. The combination also killed MDR-TB and non-resistant TB strains.

The combination in an elegant solution to a vexing problem of TB treatment: the TB bacterium produces an enzyme called beta-lactamase that destroys penicillin-like antibiotics. This required the development of new drugs to treat the disease, most of which were developed in the 1950s and 60s. However, after nearly 50 years of use, TB bacteria have started to develop resistance to these drugs. So the researchers revisited the idea of using penicillin-like antibiotics against TB and developed a way to get around the problem of beta-lactamase. One of the drugs used in the combination, clavulanate, is a beta-lactamase inhibitor. The clavulanate basically acts as decoy molecule that preoccupies the beta-lactamase enzyme, allowing the other drug in the combination, a penicillin-like antibiotic called meropenem, to sneak in and kill the TB bacterium.

Two things make this finding especially exciting to researchers in the field of TB treatment. First, the drugs used in the combination treatment are FDA-approved, which should make it much easier to begin clinical trials on humans, although clavulanate is currently only commercially available in combination with other penicillin-like antibiotics such as amoxicillin.

The other exciting thing is that if this combination treatment proves effective in human, it could greatly simplify the treatment of TB. Current TB therapy requires four antibiotics that must be taken for at least six months. If a combination treatment involving just two drugs works against drug-susceptible, MDR-TB and XDR-TB, it could help could help patients better adhere to therapy and make it easier to treat TB in developing countries, where drug-resistant TB can be rampant.

Plans are underway for two clinical trials, one in South Korea beginning this year and involving approximately 100 XDR-TB patients and a separate trial to be conducted in South Africa.

For more information about TB, join the Healia Health Community for Tuberculosis.

_{Photo: Aidan Jones, Flickr, Creative Commons}