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Tuberculosis Standoff

Efforts to contain tuberculosis may only be making the bugs behind the disease stronger, writes Sally Lehrman at Scientific American, and not just because of antibiotic resistance. Genetic studies indicate that even successful treatment and vaccines to prevent the disease could be pressuring the bacterium to be more dangerous, she adds.

TB often remains a latent infection until something, such as another infection, triggers its activation. Recent genetic studies of the disease have divvied tuberculosis into a number of families, some of which led to more aggressive disease. In addition, Lehrman writes that aggressive strains may be taking roots as treatments better address milder TB cases. "This divergent effect would allow the more aggressive, faster-spreading bacterial families to establish a stronger foothold," Lehrman writes.

Another genetic study of the genes encoding the bug's outer proteins showed that they haven't changed much — something most other pathogens do to avoid detection by the host immune system. Vaccines to prevent TB often amp up the body's immune response to the bacterium, but for this disease, Lehrman says, that has the unintended effect of making things worse as the response to the disease is often what causes the most damage. "A family of bacteria that has evolved to boost the immune response might be helped, not hurt, by a vaccine that has further activated the immune system of people who were inoculated," she adds.

"Maybe the goal shouldn't be to eradicate the disease," Clifton Barry from the National Institute of Allergy and Infectious Diseases tells her.

"Instead of trying to eliminate all disease-causing TB microbes, he and others propose, the aim should perhaps be to favor bacteria that are milder and more likely to stay in a dormant state," Lerhman adds. "Engineering such a successful standoff is, of course, a difficult and complex proposition."