Such a device could easily be built with existing off-the-shelf technology, says Krapf, adding that it would be no more complicated than the internal workings of a standard DVD player. The device relies on specialized surface chemistry that avoids protein adsorption, except for those molecules that need to be detected. Then, the presence of these molecules is recorded by fluorescence using a red diode laser.
Once detected, TB infections are generally treatable with a long course of antibiotics, and one of the basic strategies behind the World Health Organization's current efforts to curb the spread of the disease worldwide is to simply find the people who are infected and get them the antibiotics they need.
The CSU development could one day play a role in curbing the spread of TB. Currently, finding people who are infected is not so simple. Doctors can spot suspected cases by taking chest X-rays, which may reveal evidence of infection in the lungs. Or they can turn to a century-old technique called a sputum smear, where a sample of coughed fluid is stained and examined under a microscope for indications of the infection. Better yet, if doctors can grow cultures of TB bacteria from lung fluid, they definitively know that a person is infected.
These tests may not detect latent TB infections, however, because people who are latently infected may not have enough bacteria in their lungs to detect. For people with latent infections, other tests exist, but they have their problems as well. A simple skin test exists, but it is only sensitive enough to detect about half of all cases, says Krapf. Other more sophisticated methods that rely upon detecting specific markers in the blood are more sensitive, but they require special facilities and training that would be far too expensive for widespread use in the developing world.
Krapf and his colleagues have been able to demonstrate the feasibility of detecting markers of TB infections at
|Contact: Angela Stark|
Optical Society of America