The growing prevalence of drug-resistant tuberculosis is a "potentially explosive situation," the World Health Organization's director general, Margaret Chan, said today at the opening of a three-day meeting on the problem.

Representatives from 27 countries affected by multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) are gathering in Beijing to discuss how to address the trend. MDR-TB is resistant to first-line drugs; XDR-TB doesn’t respond to those meds or second-line therapies. More than 500,000 MDR-TB cases occur annually—only 3 percent of them treated according to WHO standards—and XDR-TB exists in more than 50 countries, the agency says. People with HIV, whose immune systems are already weakened by the AIDS-causing virus, are at increased risk of TB.

Curing tuberculosis that's resistant to the most commonly used, first-line drugs is a growing problem, with an estimated half million people worldwide now infected with so-called MDR (multi-drug resistant) TB. Of those, an estimated 50,000 have extensively drug-resistant (XDR) strains that don't respond to more potent drugs, either. Now scientists say they've hit upon a potential breakthrough: an antibiotic previously dismissed as useless against TB killed 13 resistant strains of the bacteria in the lab when it was combined with another drug.

The finding, published today in Science, has yet to be tested in people, study co-author John Blanchard, a biochemistry professor at Albert Einstein College of Medicine in New York, tells ScientificAmerican.com. But in a Petri dish, the meds, meropenem and clavulanate, destroyed and stopped the replication of the resistant TB bacteria, cultured from mucus samples from South Korean patients.

Is Pres. Obama getting closer to filling a key health post? The role of Food and Drug Administration (FDA) chief is down to two candidates, the Washington Post says in an unsourced report: Baltimore Health Commissioner Joshua Sharfstein and former New York City Health Commissioner Margaret Hamburg. Sharfstein's name has been floated repeatedly since Obama was elected, and Hamburg's surfaced early this month.

A 30-year-old Colombian woman with damaged airways is healthy months after receiving what European doctors are reporting is a first-ever, stem-cell-based windpipe transplant. They say the technique has allowed the woman to thrive without the use of the drugs that other transplant patients must take to prevent their immune systems from rejecting the new organs.

The unique transplant was performed in June on Claudia Castillo, who was severely short of breath after part of her trachea had collapsed from tuberculosis, hampering the flow of oxygen to her left lung. Doctors in Barcelona took a trachea from a 51-year-old female donor who’d died of a stroke and, over a six-week “washing,” stripped it of its cells. British doctors then grew stem cells from Castillo’s own bone marrow in the lab and had them grow on the donor trachea with them before implanting it, creating a kind of hybrid windpipe with the donor organ as a scaffold, the doctors write in this week’s edition of The Lancet.

Good news for potheads making their annual trek to Black Rock, Nev. this week to celebrate Burning Man: A new study says that marijuana appears to fight infections. According to research published in the Journal of Natural Products, the five most common cannabinoid compounds in weed—tetrahydrocannabinol (THC), cannabidiol, cannabigerol, cannabinol and cannabichromene—can kill antibiotic-resistant bacteria. Think MRSA (methicillin-resistant Staphylococcus aureus), which claimed more lives than AIDS in 2007 or, more recently, extensively drug-resistant mycobacterium tuberculosis (XDR-TB.)