Healthcare Workers at Risk for Drug-Resistant TB
At yesterday’s symposium on drug-resistant tuberculosis and prevention at the American Society of Tropical Medicine and Hygiene annual meeting, Harvard Medical School’s Edward Nardell recalled the “old days” of TB. In the 1930s at Bellevue Hospital in New York City, every year, one-third of the nursing class would get TB. By the end of their third year in nursing school, 100 percent of the students had latent TB infection, with 10 percent developing active disease. Of course, that was before antibiotics.
These days, most of us can’t remember a time before antibiotics. But, with growing resistance to the antibiotics we’ve come to rely on, healthcare workers are once again at risk of developing drug-resistant TB.
Multidrug resistant TB (MDR-TB) survivor and South African physician Dalene von Delft shared her sobering story of contracting multidrug-resistant TB in Cape Town in 2010. One of her biggest fears during treatment was that she would permanently lose her hearing, a common side effect of one of the MDR-TB drugs. She listened to music nonstop for days, just in case. She knew that if she lost her hearing she wouldn’t be able to use a stethoscope, and would have to find a new career. Fortunately, she was able to access a new drug, bedaquiline, through compassionate use. She was one of only four patients in South Africa who had access to it. After over 18 months of treatment, she was cured of MDR-TB and her hearing remained intact.
Today, Von Delft uses her personal experience to educate medical students about the risk of contracting TB, and how they can best protect themselves in work environments with few institutional controls in place, such as an enforced protocol on mask wearing.
The number of annual multidrug-resistant (MDR) TB cases is on the rise and so-called totally drug-resistant TB is emerging in both India and southern Africa. According to the recently released 2013 Global Tuberculosis Report, nearly four percent of all new TB cases are drug-resistant.
At the same time, extensively drug-resistant (XDR) strains of TB have now been identified in 92 countries. Von Delft compares XDR-TB (extensively drug-resistant TB) to a lung cancer that spreads through the air we breathe. It has a less than 20 percent cure rate.
With a growing interest in global health, more people from low-incidence countries are traveling to areas with high TB rates. This poses the question: How can healthcare workers be protected?
Yesterday’s session at ASTMH, “Drug-Resistant Tuberculosis: Steps forward for Prevention,” explored various obstacles and potential solutions to prevent the spread of drug-resistant TB, from educating medical students about the risks, to developing more rapid diagnostics and new vaccines.
Nardell emphasized the special risk to healthcare workers, medical students and others who may be traveling from low-incidence settings to high-incidence settings. Nardell once had a student ask how to be protected while traveling to an area with a high incidence of TB, and he told them to choose a different project. There are preventative measures, such as good ventilation, surgical masks for patients and respirators for healthcare workers, but they’re not foolproof.
Often patients in tuberculosis wards, where most preventative measure are taken, are being treated properly and are no longer infectious. But, paradoxically, Nardell explained that most people with infectious TB don’t know they have it, so the biggest risk to healthcare workers may be the patient who comes in with a broken bone or a pregnancy—and who unknowingly also has TB.
“Ideally, we need a vaccine to prevent our healthcare workers from getting ill,” Von Delft said.
New data shows that the 90-year-old infant vaccine BCG may offer short-term protection to adults. A study is planned to see if BCG provides protection from infection for healthcare workers and others traveling to TB-endemic areas.
Lewellys Barker, senior medical advisor at Aeras, presented on progress in TB vaccine research and development. A better vaccine would protect against all forms of tuberculosis, including MDR and XDR. Developing new TB vaccines is a long and difficult process, though, because it’s unclear what immune response is needed. Aeras and other partners in TB vaccine R&D are identifying new antigens and platforms, emphasizing a diversity of candidates in the pipeline, and working to improve animal models for TB vaccines.
Barker stated that the development of new vaccines is symbiotic with the development of other much-needed new tools. Research is being done to see how new TB vaccines could work in combination with drug therapies to treat, as well as prevent, TB. And clearer diagnostics are crucial to improving clinical trial results.
David Alland from the University of Medicine and Dentistry of New Jersey presented on molecular TB drug resistance testing using GeneXpert, which can diagnose TB and test for rifampicin resistance in less than two hours.
The symposium was chaired by Naomi Aronson, of Uniformed Services University of the Health Sciences and Thomas Evans of Aeras.
Healthcare workers put themselves at risk every time they are exposed to drug-resistant TB. The development of adequate protective measures is crucial, and according to Barker, “there are reasons to be optimistic.”