Patients are treated at a government tuberculosis hospital in Gauhati,… (Anupam Nath / Associated…)
Doctors are tracking at least a dozen cases of "totally drug-resistant" tuberculosis in India. How did the resistant strains develop, and how will public health officials respond?
Dr. Otto Yang of the Geffen School of Medicine at UCLA spoke with Booster Shots about drug-resistant TB.
Physicians in India reported discovering a strain of tuberculosis that is “totally drug-resistant.” How are such strains discovered?
It is routine to test the TB bacteria for sensitivity to panels of drugs when treating patients, because resistance against individual drugs happens so commonly. Clinicians use this information to choose the best combinations of medications and avoid ones to which the bacteria are resistant.
How would a pathogen develop that kind of resistance?
Resistance tends to develop when the bacteria are partly treated. Resistance requires mutations, and mutations require bacterial replication, and bacterial replication requires incomplete treatment.
Are there specific things about tuberculosis that make it an especially good candidate for developing drug resistance?
Because TB is so widely distributed worldwide, including in resource-limited areas where treatment is difficult and inconsistent, this gives TB the opportunity to find these conditions.
How does TB affect victims? Are certain patients at higher risk to get the disease -- and to die from it -- than others?
The most common infection is the lungs, where it is first inhaled. However, it can be found anywhere in the body. Usually the immune system keeps it suppressed, but in people who get weak immune systems due to age or disease (such as AIDS) or medications (to treat autoimmune diseases or prevent transplanted organ rejection), TB can reactivate and affect any part of the body, from lungs to brain to adrenal glands ... anywhere.
How much of a danger does this drug-resistant TB pathogen pose to people in India and around the world?
This depends on how widespread it becomes. Obviously it could be devastating if it spreads, because treatment options are so limited. So far it seems not to have been as contagious as other strains, possibly because the mutations required to make it drug-resistant also make it a little less virulent.
What are the options for public health officials in India now? Will they need to set up quarantines?
Best option is to quarantine while the patients are infectious, which is standard for regular TB, too. Most important is monitoring that therapy is being given consistently, to prevent sensitive TB from becoming resistant, and to contain resistant TB.
How about officials in other countries? Are there defensive strategies in place to keep the drug-resistant TB from spreading here?
Certainly testing of TB isolated from persons with active disease is necessary to identify people with resistant TB. The best way then to prevent further spread is monitored therapy, to reduce the organisms and, therefore, risk of spread.
Are there new drugs coming to combat difficult-to-treat TB? Can you describe what they are, how they work?
Yes, there are new drugs in the pipeline, but too few. Generally, at least two drugs with good activity need to be given together. Also, old drugs that are rarely used because of toxicity and lower efficacy are now being brought back to the clinic.
Are there other infectious agents that have evolved, or are feared to soon evolve, to be “totally drug-resistant?” What are they, and what can we do about them?
Many regular bacteria are growing in resistance, due to overuse and misuse of antibiotics. Current Methicillin-resistant Staphylococcus aureus, or MRSA, is sensitive to mainstay drugs like vancomycin, but there are now rare cases of MRSA that show reduced sensitivity to this and other drugs, severely limiting treatment options. A bacterium called Acinetobacter has become very resistant, with some strains limited to one drug of our whole arsenal of antibiotics. Some strains of Pseudomonas have become pan-resistant.
This interview has been edited for clarity. Return to the Booster Shots blog.