Bacteria found to thrive on frontline anti-T.B. drug

The war pitting researchers and clinicians against a growing array of tuberculosis bacteria strains that are resistant to one of more antibiotics has taken a disturbing turn.

U.S. and Chinese researchers reported Monday a strain of bacteria that is not only immune to one of the main drugs in the anti-tuberculosis arsenal, it actual grows better in the presence of the drug.

In a study to be published in the January 2010 issue of The International Journal of Tuberculosis and Lung Disease, researchers from the Johns Hopkins Bloomberg School of Public Health, Chongqing Pulmonary Hospital, Lanzhou University and Fudan University report on a strain of the tuberculosis bacterium found in a Chinese man.

The 35-year-old man was being treated with a combination of rifampin and two other frontline anti-T.B. drugs recommended by the World Health Organization. Rifampin is a drug doctors often use to treated mycobacterium infections such as tuberculosis, leprosy and some forms of meningitis.

As the man's condition continued to worsen, doctors began treating him with rifampin and a pair of second-tier drugs, again with little success.

In the laboratory, the bacteria thought to be causing the man's tuberculosis grew poorly in a culture medium lacking rifampin. When the antibiotic was add to the growth medium, the bacteria thrived.

The study by the Hopkins and Chinese researchers is thought to be one of the first reports of a rifampin-resistant - or more accurately rifampin-dependent - strain of tuberculosis bacterium.

"Rifampin-dependent tuberculosis is an unrecognized and potentially serious treatment issue," said Dr. Ying Zhang, senior author of the study and professor in the Bloomberg School's W. Harry Feinstone Department of Molecular Microbiology and Immunology.

Zhang called the prospect of rifampin-resistant T.B. "ominous." Further research is "urgently needed" into the phenomenon and what role it might be playing in the spread of multidrug-resistant tuberculosis and the failure of tuberculosis treatment, he said.

The WHO estimates that tuberculosis kills about 2 million people worldwide each year.