Many advanced rapid diagnostic tests don’t detect multi-drug resistant TB strain from Swaziland
Researchers from Epicentre and Research Center Borstel analyzed samples of TB strains from 2009-2010, when the most recent national TB drug resistance survey took place in Swaziland. Thirty percent of the 125 different MDR-TB strains contained a specific genetic mutation -- rpoB (I1491F) -- that is the same mutation previously identified in rare strains found in Australia and Hong Kong.
“These diagnostic tests are our front line of defense in fighting drug-resistant TB,” Doctors Without Borders' HIV/TB referent Alex Telnov said. “Accurate, rapid test results mean that we can start people on treatment that targets the specific strain they are infected with, which in turn increases their chances of survival and helps prevent transmission of drug-resistant infections. To learn that we could be missing so many cases means there is an urgent need to adapt our detection approach to MDR-TB in Swaziland.”
The tests, including the XpertMTB/RIF assay that is recommended by the World Health Organization, are the first step to controlling the illness. Due to its high proportion of the circulating strain, experts say I491F mutations pose a significant public health challenge that must not be ignored, as the likely consequence is further transmission of this difficult-to-treat strain.
"If we’re facing wide distribution of this strain in Southern Africa or elsewhere, it is imperative that the rapid molecular tests we currently use, as well as those under development, be adapted to detect a wider range of mutations," Epicenter researcher Maryline Bonnet said.