Tiny Tool Can Play Big Role Against Tuberculosis

Photo: Microscope

The quest for a low-cost, simple,
effective method led back to the
trusty microscope; © Christian

“We are hopeful that this more sensitive method, which is both simple and inexpensive, will improve diagnosis in patients,” said lead researcher Doctor Kevin Fennelly of the UF College of Medicine.

The new technique, which involves vacuum filtering a sputum sample treated with household bleach and other simple chemicals through a small filter, could dramatically improve TB diagnoses globally, particularly in settings where the disease is common and resources are limited. It is especially useful when the presence of only a small number of bacteria in the test sample makes it hard to detect TB. The researchers are refining the technique in hopes of developing a cost-effective product that can be used globally.

TB is a treatable disease caused by a microbe called Myocardium tuberculosis. It most often affects the lungs, but can also target organs such as the brain, spine and kidneys. Symptoms of active disease include a chronic cough, sputum production and coughing up blood. TB spreads from person to person through the air.

Once the leading cause of death in the United States, TB has been largely under control in Western nations. Still, more than 11,000 U.S. cases were reported in 2010, the latest year for which there is comprehensive data. That year, almost 9 million people around the world were diagnosed with TB and almost 1.5 million died from it. TB causes more deaths than any other bacterial infection and is the most common killer of people living with HIV.

“TB is still a tremendously important disease worldwide and control efforts are greatly hindered by lack of simple, inexpensive diagnostics that could be used at the point of care,” said Doctor Elizabeth Talbot, a Dartmouth College infectious diseases and TB diagnostics expert. “What Fennelly has done is capitalise on existing infrastructure of microscopy to try to improve performance of that prevalent diagnostic tool.”

The most widely used way to confirm TB infection is to use a microscope to identify and count disease-causing bacteria in sputum smeared onto a glass slide. This so-called direct-smear method also helps health professionals figure out how likely people are to pass on the disease, what treatment decisions should be made, and how well patients are responding to treatment. Although the method has been in continuous use for more than a century, it can be unreliable, catching cases only about half of the time, on average.

Part of the problem is that sometimes sputum samples do not contain many bacteria, making it hard to detect TB. Concentrating bacteria onto a small area could help improve detection accuracy, and although previous efforts have led to improvements, they tend to require expensive equipment or technical know-how. In some cases, gains were offset by loss of sample or safety concerns. So the quest for a low-cost, simple, effective method led back to the trusty microscope.

MEDICA.de; Source: University of Florida