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| After conducting public health research in Peru for 20 years, Tulane pediatrician Richard Oberhelman is focusing on pediatric tuberculosis. (Photos by Paula Burch-Celentano) |
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An international team of researchers working in Peru has concluded that a new method for diagnosing tuberculosis, the Microscopic-Observation Drug Susceptibility (MODS) assay, is faster and more reliable than current standard tests for the disease. The team's study results were published recently in the New England Journal of Medicine.
"MODS will benefit developing countries that have been fighting the spread of new varieties of drug-resistant tuberculosis," says Richard Oberhelman, a pediatrician and clinical associate professor of tropical medicine at the Tulane University School of Public Health and Tropical Medicine. Oberhelman has been conducting public health research in Peru for 20 years, focusing most recently on pediatric tuberculosis. He is a member of the Peru Working Group assessing the diagnostic capabilities of MODS.
"By the 1970s, tuberculosis was on the decline as a public health problem," says Oberhelman. "We had decent treatments and a good treatment strategy."
Then, in the 1980s, AIDS started to spread and public health resources were reallocated to confront the epidemic. Tuberculosis was neglected and it began to re-emerge, especially in developing countries. Drug-resistant varieties of tuberculosis developed, and individuals with AIDS were much more likely to develop full-blown cases of tuberculosis.
The MODS technique shows promise as a tool in the renewed fight against tuberculosis, according to the recent study. Currently available tuberculosis tests can take from two to three weeks or even longer to provide a definite diagnosis. By contrast, MODS enables technicians to identify tuberculosis in an average of seven days, approximately half the time required for the standard methods, and the study demonstrated that MODS results were more reliable.
Where standard tests use a gel medium for culturing samples from the patient, MODS relies on growing samples in a liquid medium. The distinctive growth patterns of the bacterial colonies can then be observed microscopically in the translucent medium.
The MODS method also allows technicians to determine at the same time what drugs the bacteria are sensitive to. Samples from the patient are cultured with antibiotics, and the results indicate which drug or drugs can be used to treat the patient effectively.
"The nice thing about MODS is that it is very inexpensive, and that can be a real help for developing countries," says Oberhelman. "In the United States there are automated systems, such as BACTEC. These systems pick up culture growth pretty fast, but they are expensive, and Peru can't afford $70,000 for such a system. The idea is to develop a method that produces rapid results at a cost that is affordable."
