In 2012 on average 1 in 30 of new TB cases worldwide was multiresistant, with peaks of 1 in 3. With patients relapsing after a first cure, on average 1 in 5 was multiresistant, with peaks up to 65%. The highest numbers were all registered in the former Soviet Union. Without active measures the numbers will only rise.
If we want to prevent an epidemic of difficult to treat tuberculosis, then resistant cases, which do not react to the normal treatment, need to be recognized as early as possible, and immediately treated with second-line antibiotics that still work. But the laboratory tests to identify resistant TB bugs are cumbersome the WHO estimates that in 2009 only 11% of multiresistant cases were discovered.
Checking smears under the microscope still is the recommended technique for TB screening, but it cannot differentiate between living and dead bacilli. So you do not know if you are looking at the cadavers of a successful treatment, or at resistant survivors. Only if the numbers after a long wait still don't fall, you know you are dealing with a resistant strain. But all that time the patient has remained contagious.
With high-tech PCR technology one can immediately ascertain if the bacillus is from a resistant strain, but in practice and certainly in resource-limited countries this is unfeasible. It also is impossible to cultivate every sample and then bombard it with every possible antibiotic to survey which ones still work for that individual patient.
Armand Van Deun and colleagues therefore gave a new application to a forgotten technique: vital staining with fluorescein diacetate (FDA). It only stains living TB bacilli, so
|Contact: prof Bouke De Jong|
Institute of Tropical Medicine Antwerp