Scientists say they've found a cure for the deadliest, most drug-resistant form of tuberculosis, known as XDR-TB, in the form of a three-drug regimen with a 90-percent success rate.

A small clinical trial, nicknamed Nix-TB, has 109 patients enrolled, but the U.S. Food and Drug Administration is rushing to approve the last of its three drugs, pretomanid, as long as it used in conjunction with the other two previously approved ones, bedaquiline and linezolid.

Tuberculosis has surpassed AIDS to become the world's leading infectious cause of death, and the XDR strain is the deadliest. There are about 30,000 XDR-TB cases in over 100 countries, and experts believe 75 percent of patients die before even receiving a diagnosis. While the typical treatment is 40 daily pills taken for two years, the new regimen requires only five pills a day for six months, and most of the side effects are manageable.