Study: TB Meds Promote Mutant Strains

Current efforts to reduce tuberculosis (TB) death tolls in areas with high rates of HIV infection promote the development of drug-resistant strains of the deadly disease, according to a study by Harvard School of Public Health researchers.

Instructor in Medicine Theodore H. Cohen and Assistant Professor of Epidemiology Megan Murray will publish their findings in the May 2 issue of the Proceedings of the National Academy of Sciences.

The new study puts an emphasis on areas with high HIV rates and warns against the effects of indiscriminately using isoniazid on all patients, Cohen said.

Isoniazid preventive therapy, a drug treatment that reduces the rate at which latent TB becomes active, is increasingly being used to battle TB in areas with high rates of HIV. However, multi-drug resistant TB, defined as “resistant to isoniazid plus at least one other first-line antibiotic,” is becoming more common, according to Cohen,

Currently, diagnosis of TB does not sufficiently distinguish multi-drug resistant TB infection from other infections, resulting in treatment of isoniazid-immune TB with isoniazid, Murray said.

Unless changed, such use of isoniazid preventive therapy “would rapidly accelerate the drug resistance of TB,” Murray said.

While isoniazid saves lives, Murray said, this form of preventative therapy should be used selectively.

Health officials should implement measures to diagnose multi-drug resistant TB and treat it separately, Cohen said.

But such procedures would be expensive and, according to Murray, measures to implement better treatment could face opposition.

TB infects two billion people, about a third of the world’s current population, according to the National Institutes of Health. About 90 percent of those infected have latent tuberculosis, Murray said. The remaining 10 percent have active tuberculosis. Active tuberculosis has a mortality rate of about 50 percent, according to the Centers for Disease Control.

Since HIV compromises its victims’ immune systems, HIV-positive patients are more susceptible to TB. As a result, TB poses a particularly large threat in areas where a significant portion of the population has HIV. In such areas, Murray said, “Infection rates are just rocketing.”