INFECTIOUS DISEASE: Racing to Defuse a Bacterial Time Bomb

Once ignored as an obscure disease, melioidosis and the frighteningly versatile bacterium that causes it are drawing attention as a bioterror threat

Grim prognosis. Burkholderia pseudomallei colonies in a blood agar dish. CREDITS: R. STONE/SCIENCE

UBON RATCHATHANI, THAILAND--A Thai man with lank black hair and grizzled stubble lolls on a cot parked in a hallway outside a crowded ward. The 61-year-old farmer answers tersely as a senior physician, Wipada Chaowagul, quizzes him. When the man was admitted on 9 May with sepsis and an abscess in his chest wall, Wipada fingered an old nemesis: melioidosis. But although nearly nine out of 10 melioidosis patients in Thailand with septic shock die, somehow the farmer beat the odds. After spending 2 months in Sappasithiprasong Hospital here in northeastern Thailand, the taciturn man with watery eyes is almost well enough to go home.

Wipada can't explain how the farmer, who suffers from kidney disease, managed to fend off a bacterium, Burkholderia pseudomallei, that in its fiercest incarnation kills most of its victims. Indeed, there is no shortage of scientific puzzles surrounding melioidosis. Over the 2 decades that Wipada has studied the once-obscure malady, more and more experts have become intrigued by the ability of B. pseudomallei to alter its form and survive in environments as disparate as soil, distilled water, and the human body.

"There's something incredibly interesting and important going on with pseudomallei, and nobody knows what that is," says Colin Manoil, a geneticist at the University of Washington, Seattle.

Melioidosis is largely confined to Southeast Asia and northern Australia and, fortunately for the rest of the world, researchers don't anticipate the shape-shifting bug breaking out of its ecological cage anytime soon. But its characteristics make it an insidious threat as a bioweapon. The bacteria can hide in the body for decades. Once the time bomb detonates, a constellation of symptoms allows melioidosis to masquerade as other ailments. Although many patients are rushed to the hospital with acute disease, others have symptoms more akin to tuberculosis or cancer, says Sharon Peacock of the Mahidol-Oxford Tropical Medicine Research Unit (MORU) in Bangkok. Misdiagnosis can prove fatal: B. pseudomallei is impervious to all but a few antibiotics.