Antibiotic combination could treat resistant TB: study

Two already existing drugs to fight bacterial infections could combine to help treat the most deadly form of tuberculosis, according to a study published Friday.

Researchers discovered a two-drug combination that blocks the growth of 13 strains of extensively drug-resistant tuberculosis (XDR-TB) isolated in a laboratory, said the study published in the journal Science.

One of the oldest known infections, tuberculosis kills approximately 1.5 million people each year. About one-third of the world's population is infected with TB.

The bacterium Mycobacterium tuberculosis, which causes the disease, has become more resistant to standard antibiotic treatment. Current TB treatments require taking four antibiotics for at least six months.

The significant increase in active TB cases since the 1980s is also due to the AIDS pandemic, said the researchers from the Albert Einstein College of Medicine of Yeshiva University and the National Institutes of Allergy and Infectious Diseases (NIAID).

One of the drugs they studied, clavulanate, inhibits the bacterial enzyme beta-lactamase, which usually protects tuberculosis bacteria from the other antibiotic, meropenem, which comes from the beta-lactam class of antibiotics.

Penicillin, the first antibiotic discovered, is a beta-lactam antibiotic.

Clavulanate is not currently commercially available except in combination with beta-lactam antibiotics like amoxicillin. Amoxicillin/clavulanic acid and meropenem are already being used to treat infections in children and adults.

"If proven in human subjects, the ability to simplify treatment to just two drugs that work against drug-susceptible, multi-drug resistant and XDR-TB could help patients better adhere to therapy," said biochemist John Blanchard of Einstein College, one of the lead authors of the study.

"This discovery could be one of the most promising developments in TB research since the discovery of isoniazid -- it is very exciting," said William Jacobs, associate director of the Einstein-Montefiore Center for AIDS Research, referring to the first effective antituberculosis medication discovered in the 1950s.

"We see tremendous potential for treating not only XDR-TB cases, but also routine TB cases," said Brian Currie, assistant dean for clinical research at Einstein College.

Bolstered by the encouraging lab results, the researchers hope to launch trials of the drug combination on a limited number of TB patients in South Korea and South Africa later this year.

Multi-drug resistant TB represents about six percent of cases diagnosed worldwide each year and are particularly prominent in countries from the former Soviet Union, Japan, South Korea and South Africa. The disease also often affects people infected with AIDS.